Photopolymerized silica sol–gel monoliths functionalized with boronic acid ligands have been developed for protein and peptide separations in polydimethylsiloxane microfluidic devices. Pore size characterization of the monoliths was carried out with scanning electron microscopy, image analysis, and differential scanning calorimetry to evaluate both the micron-sized macropores and the nanometer-sized mesopores. Monoliths were functionalized with boronic acid using three different immobilization techniques. Batch experiments were conducted to determine the capacity of the monoliths and selectivity toward cis-diol-containing compounds. Conalbumin was used as a model glycoprotein, and a tryptic digest of the glycoprotein horseradish peroxidase was used as a peptide mixture to demonstrate proof-of-concept extraction of glycoproteins and glycopeptides by the monoliths formulated in polydimethylsiloxane microfluidic chips. For proteins, fluorescence detection was used, whereas the peptide separations employed off-line analysis using matrix-assisted laser desorption ionization mass spectrometry.

Advanced solid-phase extraction with molecularly imprinted polymers (MIP) was used in this study. A noncovalent imprinting approach was applied to separate 17β-estradiol, estriol and estrone from water samples. Polymer material was prepared by bulk polymerization with methacrylic acid as a functional monomer, divinylbenzene and ethyleneglycol dimethacrylate as crosslinkers, and acetonitrile, acetonitrile/toluene (3:1, v/v) or isooctane/toluene (1:99, v/v) as a porogen. We also prepared a MIP film on a silica gel surface with methacrylic acid and ethyleneglycol dimethacrylate as a monomers and acetonitrile as a solvent. Qualitative and quantitative hormone analyses were carried out by HPLC with various detection techniques, including UV/visible spectroscopic detection [diode array detection (DAD)] and electrochemical detection (CoulArray).

Vitex trifolia L. is an important Indian medicinal plant with diverse pharmacological properties. In a recent study, we reported the isolation and antitubercular activity evaluation of three new diterpenoids from its leaves; here we have developed a validated rapid, simple, precise and accurate high-performance TLC (HPTLC) method for the simultaneous quantification of isolated diterpenoids in V. trifolia. Diterpenoids, 6α,7α-diacetoxy-13-hydroxy-8(9),14-labdadien (A), 13-hydroxy-5(10),14-halimadien-6-one (B) and 9-hydroxy-13(14)-labden-16,15-olide (C) were separated on silica gel 60F₂₅₄ HPTLC plates using chloroform: acetone (98:2 v/v) as mobile phase. The quantitation of diterpenoids was carried out using densitometric reflection/absorption mode at 610 nm after post-chromatographic derivatization using a vanillin–sulfuric acid reagent. A precise and accurate quantification can be performed for compounds A and B in the linear working concentration range of 333–1000 ng/band and for C in the range of 670–2000 ng/band with good correlations (r = 0.9984, 0.9991 and 0.9994, respectively). The method was validated for peak purity, precision, accuracy, robustness, limit of detection and quantitation, as per the ICH guidelines. The method reported here is simple, reproducible and may be applied for the quantitative analysis of above diterpenoids in the leaves of V. trifolia.

This paper describes the isolation of flavonoids and other aromatic compounds from an ethyl acetate extract of leaves of Siparuna glycycarpa using stepwise elution counter-current chromatography (CCC). The elution profile yielded the following compounds: diglycosylated flavonoids, quercetin 3-O-rutinoside and quercetin 7-O-rutinoside, followed by monoglycosylated flavonoids, kaempferol-3-O-β-glucopyranoside, kaempferol-3-O-β-rhamnopiranoside, kaempferol-3-O-β-6’’(p-coumaroyl) glucopyranoside, and quercetin-3-O-β-glucopyranoside, and then free phenolics, protocatechuic acid and 2’,6’-dihydroxy-4, 4’-dimethoxydihydrochalcone, which shows that this type of elution covers a broader range of polarity than the traditional isocratic mode. This makes it more suitable to perform separations of mixtures containing large differences in hydrophobicity. A GC analysis of a blank CCC run was performed to determine if changes in the mobile phase composition affect the chromatographic process. Results showed a gradual variation of the composition of the mobile phase emerging after the step gradient, favoring the selectivity of the solvent system.

A simple, robust, and rapid LC–MS/MS method has been developed and validated for the simultaneous quantitation of clopidogrel and its active metabolite (AM) in human plasma. Tris(2-carboxyethyl)phosphine (TCEP) was used as a reducing agent to detect the AM as a disulfide bonded complex with plasma proteins. Mixtures of TCEP and human plasma were deproteinized with acetonitrile containing 10 ng/mL of clopidogrel-d4 as an internal standard (IS). The mixtures were separated on a C₁₈ RP column with an isocratic mobile phase consisting of 0.1% formic acid in acetonitrile and water (90:10, v/v) at a flow rate of 0.3 mL/min. Detection and quantification were performed using ESI-MS. The detector was operated in selected reaction-monitoring mode at m/z 322.0→211.9 for clopidogrel, m/z 356.1→155.2 for the AM, and m/z 326.0→216.0 for the IS. The linear dynamic range for clopidogrel and its AM were 0.05–20 and 0.5–200 ng/mL, respectively, with correlation coefficients (r) greater than 0.9976. Precision, both intra- and interday, was less than 8.26% with an accuracy of 87.6–106%. The validated method was successfully applied to simultaneously analyze clinical samples for clopidogrel and its AM.

Slip flow has become a topic of interest in reversed-phase liquid chromatography because it gives a flow enhancement that facilitates the use of submicrometer particles, providing a large improvement in separation efficiency. Moreover, slip flow provides an additional improvement in efficiency by reducing the velocity distribution in the mobile phase. The phenomenon of slip flow in open tubes is described in chromatographically relative terms. A recent paper in this journal is discussed, as it provides the first theoretical study of slip flow in packed beds, in this case for face-centered cubic geometry. The theory paper reveals that the presence of the packed bed introduces a heterogeneity in fluid velocities that is absent in open tubes, reducing the additional improvement in efficiency from slip flow. The recent paper also suggests that there is yet another factor improving efficiency, which is size-exclusion of proteins from regions of stagnant flow. The latter is supported by recently published data on restricted protein diffusion in face-centered cubic silica colloidal crystals. Extremely low plate heights are enabled by use of submicrometer particles, and further improvement appears to be possible when the analyte size is on the order of 1% of the particle diameter or larger.

A novel and rapid solventless microwave-assisted extraction coupled with low-density-solvent-based in-tube ultrasound-assisted emulsification microextraction has been developed for the efficient determination of nine organophosphorus pesticides in soils by GC analysis with microelectron capture detection. A specially designed home-made glass tube inbuilt with a scaled capillary tube was used as an extraction device to collect and measure the separated extractant phase easily. Parameters affecting the efficiencies of the developed method were thoroughly investigated. From experimental results, the following conditions was selected for the extraction of organophosphorus pesticides from 1.0 g of soil sample into 5 mL of aqueous solution under 226 W of microwave irradiation for 2.5 min followed by ultrasound-assisted emulsification microextraction with 20 μL toluene for 30 sec and then centrifugation at 3200 rpm for 3 min. Detections were linear in the range of 0.25–10 ng/g with detection limits between 0.04–0.13 ng/g for all target analytes. The applicability of the method to real samples was assessed on agricultural contaminated soils and the recoveries ranged between 91.4 and 101.3%. Compared to other methods, the present method was shown to be highly competitive in terms of sensitivity, cost, eco-friendly nature, and analysis speed.

A method for the fast analysis of a specific component in complex samples by GC–MS was developed and used for the quantitative determination of prometryn in hair samples. In this method, the tedious and time-consuming sample pretreatment for purification was saved, and a short capillary column and fast temperature program were employed to speed up the analysis. Although the measured total ion chromatogram is composed of overlapping peaks with interference and background noise, the signal of prometryn can be extracted by chemometric methods. Window-independent component analysis was used to extract the mass spectrum and a non-negative immune algorithm was employed to obtain the chromatographic profile of the interesting component from the measured data. Due to the complexity of the matrix, a standard addition method was adopted for the quantification. The applicability of the method was validated with spiked samples, and the recoveries were in the range of 99–105%.

The reduction of analysis time, cost, and improvement of separation efficiency are the main requirements in developing of high-throughput assay methods in bioanalysis. It can be achieved either by ultra high performance liquid chromatography (UHPLC) using stationary phases with small particles (< 2 μm) at high back pressures or by using opposite direction — monolithic stationary phases with low back pressures. The application of new types of monolithic stationary phases for UHPLC is a novel idea combining these two different paths.

Derivatization at the injection port following hollow-fiber-based liquid–liquid–liquid microextraction with tetramethylammonium acetate as a dual-function regent, i.e. an acceptor and derivatization reagent, for the determination of benzoic acid (BA) and sorbic acid (SA) in real samples by GC was developed. BA and SA were extracted from aqueous samples to an organic phase impregnated into the pores of the hollow fiber wall, and then back-extracted to the acceptor solution located inside the lumen of the hollow fiber. Upon injection, the extracted analytes were quantitatively derivatized to their methyl esters with tetramethylammonium acetate in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The linearity was satisfactory over a concentration range of 0.1–50 mg L⁻¹ with r > 0.993 for both analytes. The limits of detections were 2.0 μg L⁻¹ for SA and 20 μg L⁻¹ for BA. The recoveries (83–116%) and precisions (RSDs of 1.2–11.4% (n = 3)) were examined by analyzing real spiked samples. The enrichment factors of BA and SA were 300 and 425. The results demonstrated that this is a simple, rapid, accurate, and sensitive method for the determination of BA and SA in various samples.

Nine nucleosides and nucleobases, including uracil, adenine, thymine, uridine, adenosine, thymidine, cytidine, guanosine, and cordycepin in natural Cordyceps sinensis, cultured Cordyceps mycelia, and Cordyceps fruiting bodies were extracted by matrix solid-phase dispersion and determined by HPLC. The experimental conditions for the matrix solid-phase dispersion extraction were optimized. Florisil was used as dispersant, petroleum ether as washing solvent, and methanol as elution solvent. The Florisil-to-sample ratio was selected to be 4:1 and no additional clean-up sorbent was needed. The calibration curves had good linear relationships (r > 0.9997). The limits of detection and quantification were in the range of 12～79 ng mL⁻¹ and 41～265 ng mL⁻¹, respectively. The intra- and interday precision were lower than 8.3%. The recoveries were between 61.5 and 93.2%. The present method consumed less sample compared with ultrasonic extraction and heating reflux extraction. The extraction yields obtained by using the present method are much higher than those obtained by ultrasonic extraction and comparable to those obtained by heating reflux extraction.

An efficient method based on ultrasound-assisted emulsification microextraction followed by injection-port derivatization GC analysis was developed to determine 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid in natural water samples. In this procedure, 12.5 μL of 1-undecanol was injected slowly into a 12-mL home-designed centrifuge glass vial containing an aqueous sample of the analytes located inside an ultrasonic water bath. The resulting emulsion was centrifuged, and 1 μL of the separated organic solvent together with 1 μL of the derivatization reagent were injected into a GC equipped with a flame ionization detector. Several factors that influence the derivatization and extraction were optimized. Under the optimal conditions, the limits of detection were 0.33 and 1.7 μg/L for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid, respectively. Preconcentration factors of 670 and 836 were obtained for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid, respectively. The precision of the proposed method was evaluated in terms of repeatability, which was less than 5.7% (n = 5). The applicability of the proposed method was evaluated by extraction and determination of chlorophenoxyacetic acids from some natural waters, which indicated that the matrices of natural waters have no significant effect on the extraction and derivatization efficiency of this method.

Monolithic stationary phases based on octadecyl acrylate for capillary electrochromatography using different initiating systems (UV irradiation, thermal, and chemical initiation) in the presence of lauroyl peroxide as initiator were synthesized. For each initiation mode, the influence of the porogenic solvent composition on both the morphological and electrochromatographic properties of the resulting monoliths was investigated. Under optimal conditions, excellent efficiencies for the photochemically and chemically polymerized monoliths (minimum plate heights of 6.9–10.7 μm and 6.5–12.6 μm, respectively) were achieved. Thermally initiated columns gave lower efficiency values, permeabilities, and longer analysis times compared to these initiating systems. The produced monolithic stationary phases were evaluated in terms of reproducibility and gave RSD values below 9.2, 10.6, and 9.8 % for UV, thermally, and chemically initiated columns, respectively.

In this study, a platinum wire coated with poly(3,4-etylenedioxythiophen) was used as an electro-assisted solid-phase microextraction fiber for the quantification of tricyclic antidepressant drugs in biological samples by coupling to GC employing a flame ionization detector. In this study, an electric field increased the extraction rate and recovery. The fiber used as a solid phase was synthesized by the electropolymerization of 3,4-ethylenedioxythiophen monomers onto a platinum wire. The ability of this fiber to extract imipramine, desipramine, and clomipramine by using the electro-assisted solid-phase microextraction technique was evaluated. The effect of various parameters that influence the extraction efficiency, which include solution temperature, extraction time, stirring rate, ionic strength, time and temperature of desorption, and thickness of the fiber, were optimized. Under optimized conditions, the linear ranges and regression coefficients of calibration curves were in the range of 0.5–250 ng mL^-1 and 0.990–0.998, respectively. Detection limits were in the range of 0.15–0.45 ng mL^-1. Finally, this method was applied to the determination of drugs in urine and wastewater samples and recoveries were 4.8–108.9%.

The retention behaviour of amino acids was studied in hydrophilic liquid chromatography on zwitterionic stationary phases. Evaluation of the influences of acetonitrile/water content, ammonium acetate concentration and mobile phase pH values were performed. 14 amino acids were tested and they were all retained to varying extents, with poorer retention in high water content eluents. The linear relationship between the logarithm of retention factor and log (water content) indicated that adsorption dominated or at least was partly involved in the separation mechanism. Electrostatic and hydrophilic interactions also contributed to the retention of these amino acids under different separation conditions with various mobile phase pH values and ammonium acetate concentrations. Thus, the overall retention mechanism could be explained as a combination of adsorption, electrostatic and hydrophilic interactions. The magnitude and contribution of each mechanism is dependent on the nature of the analyte and the separation conditions applied.

Pesticide residue analysis is an important part of food quality control. Three of the most widely used methods are the DFG S19 (extraction with acetone), the ChemElut method (extraction with methanol) and QuEChERS (acetonitrile-based). Despite many developments in the field of sample preparation, matrix effects are still one of the most disturbing problems in routine analysis. In this study we compare the matrix effects in liquid chromatography – mass spectrometry analysis after use of these three methods in pesticide analysis. Using postcolumn infusion, we were able to visualize all suppressions over the whole chromatogram in matrix effect profiles. Recently, we also presented a system for the determination of up to 300 pesticides from various kinds of fruit and vegetables. For the measurement, we injected an aliquot of a raw acetonitrile extract. The subsequent clean-up was carried out fully automated by a multi-dimensional liquid chromatography. Matrix compounds and analytes are separated in the first dimension on a HILIC column. In this study we also compared this new approach with the classical methods. The matrix effect profiles showed less suppression with the HILIC-based clean-up. A final evaluation of the partitioning steps of all methods confirmed the benefits of the chromatographic clean-up approach.

Poly methacrylic acid-ethylene glycol dimethacrylate coated solid phase microextraction fiber coupled to gas chromatography with micro electron capture detector was developed for the determination of four chlorphenols in water samples for the first time. A novel and simple method for preparation of this novel solid phase microextraction fiber was proposed by copolymerization of methacrylic acid and ethylene glycol dimethacrylate in proper solvent using glass capillary as “mold”. The factors affecting the polymerization were optimized in detail. Furthermore, extraction performance of poly methacrylic acid-ethylene glycol dimethacrylate fiber was evaluated. Moreover, experimental headspace- solid phase microextraction parameters, such as extraction temperature, extraction time, salt concentration, stirring speed and pH, were optimized by orthogonal array experimental designs. Under the optimized conditions, the target analytes were linear in the range of 0.2–50 ng mL⁻¹, and the correlation coefficients were all greater than 0.99. Relative standard deviation was less than 8.9%, and the detection limits were in the range of 0.1–10 ng L⁻¹. Four cholorphenols were detected from tap and lake water samples using the proposed method, with the recoveries of spiked natural water samples were ranged from 91.8% to 110.8% and 90.6% to 111.4% for tap and lake water samples respectively.

The epidermal growth factor receptors are significant targets for screening active compounds. In this work, an analytical method was established for rapid screening, separation and identification epidermal growth factor receptors antagonists from Curcuma longa. Human embryonic kidney 293 cells with steadily high expression epidermal growth factor receptors were used to prepare the cell membrane stationary phase in cell membrane chromatography model for screening active compounds. Separation and identification of the retention chromatographic peaks was achieved by the high performance liquid chromatography/mass spectrometry. The acting sites, docking extents and inhibitory effects of the active compounds were also demonstrated. The screening result found that ar-turmerone, curcumin, demethoxycurcumin and bisdemethoxycurcumin from Curcuma longa could be active components in a similar manner to gefitinib. Biological trials showed that all of four compounds can inhibit epidermal growth factor receptors protein secretion and cell growth in a dose-dependent manner, down regulate phosphorylation of epidermal growth factor receptors. This analytical method demonstrated fast and effective characteristics for screening, separation and identification active compounds from complex system and should be useful for drug discovery with natural medicinal herbs.

GC column selectivity can be continuously adapted to suit analytical needs using a flow-tuneable tandem system. Its application to the separation of complex mixtures requires a deep understanding of the theory in this area. Although a number of researchers have developed specific models, a general and exhaustive theory is still missing. In this paper we have made an implementation of pre-existing models on tandem-column assemblies operated isothermally. In particular, we have investigated the effect of column length and diameter, phase thickness and oven temperature on chromatographic parameters, such as capacity factor, selectivity, and intrinsic resolution. A new approach for the correct choice of the working temperature has been proposed.

The aim of this investigation was the preparative isolation of solanidine (aglycone of the two main potato glycoalkaloids: α-chaconine and α-solanine) from fresh Solanum tuberosum (cv. Pompadour) material by implementing a new preparation scheme using centrifugal partition chromatography. A setup for obtaining solanidine by hydrolysis of the glycoalkaloids found in the skin and sprouts of S. tuberosum was first developed. Then its isolation was carried out by the development of centrifugal partition chromatography conditions: the solvent system used for separation was ethyl acetate/butanol/water in the ratio 42.5/7.5/50 (v/v/v), 0.6 g of crude extract were separated with a 8 mL/min flow rate of mobile phase while rotating at 2500 rpm. A run yielded 98 mg of solanidine (86.7% recovery from the crude extract) in a one-step separation. The purity of the isolated solanidine was over 98%. Thus, centrifugal partition chromatography has proven to be the method of choice to get solanidine of very high purity from S. tuberosum biomass in large quantities.

During HPLC-ESI-MS/MS analysis of rat submandibular saliva secreted under isoprenaline stimulation, a protein with an experimental [M+H]¹⁺ = 10544.24 m/z was detected (17.5 ± 0.7 min). The MS/MS fragmentation pattern, manually investigated, allowed establishing an internal sequence in agreement with a DNA-derived sequence of an unknown rat protein coded D3Z9M3 (SwissProt). To match the experimental MS/MS fragmentation pattern and protein mass with theoretical data, the removal from the N-terminal of the signal peptide and from from the C-terminal of three a.a. residues (Arg-Ala-Val) and the cyclization of the N-terminal glutamine in pyroglutamic had to be supposed, resulting in a mature protein of 90 a.a. HPLC-ESI-MS/MS of the trypsin digest ensured 100% sequence coverage. For the high glutamine content (34/90 = 37.8%) we propose to name this protein rat gliadoralin A 1–90. Low amounts of 5 different isoforms were sporadically detected, which did not significantly change their relative amounts after stimulation. Gliadoralin A is substrate for transglutaminase-2, having Lys 60 and different Gln residues as major determinants for enzyme recognition. In silico investigation of superior structures evidenced that a small part of the protein adopts an α-helical fold, whereas large segments should be unfolded, suggesting an unordered conformation.

Protein extraction is a crucial step for proteomics studies. To establish an effective protein extraction protocol suitable for 2-DE analysis in Jerusalem artichoke (Helianthus tuberosus L.), three different protein extraction methods—trichloroacetic acid/acetone, Mg/NP-40, and phenol/ammonium acetate methods were evaluated using Jerusalem artichoke leaves as source materials. Of the three methods, the trichloroacetic acid/acetone method yielded the best protein separation pattern and highest number of protein spots in 2-DE analysis. Proteins highly abundant in leaves, such as Rubisco, are typically problematic during leaf 2-DE analysis, however, and this disadvantage was evident using trichloroacetic acid/acetone. To reduce the influence of abundant proteins on the detection of low abundance proteins, we optimized the trichloroacetic acid/acetone method by incorporating a PEG fractionation approach. After optimization, additional 363 (36.2%) protein spots were detected on the 2-DE gel. Our results suggest that trichloroacetic acid/acetone method is a better protein extraction technique than Mg/NP-40 method and phenol/ammonium acetate method in Jerusalem artichoke leaf 2-DE analysis, and that the trichloroacetic acid/acetone method combined with PEG fractionation procedure is the most effective approach for leaf 2-DE analysis of Jerusalem artichoke.

Benzoylurea insecticides are a kind of important pesticides and have contributed great to the output of crops. Their residue in environment put serious threats on the human health and environmental safety. Present study established a new, rapid and reliable method for the monitoring of typical benzoylurea insecticides such as diflubenzuron, flufenoxuron, triflumuron, and chlorfluazuron with dispersive liquid-liquid microextraction prior to high performance liquid chromatography. Chlorobenzene and ethanol were employed as the extraction solvent and disperser solvent, respectively. The possible parameters which would influence the extraction efficiency such as the kinds and volumes of extraction and disperser solvents, extraction time, sample pH, centrifuging time, and salting-out effect were optimized in detail. Under the optimal conditions, the linear range of proposed method was in the range of 1.0 – 70 μg L⁻¹. The detection limits varied from 0.24 μg L⁻¹ to 0.82 μg L⁻¹ and the precision of the method was below 6.5% (RSD, n = 6). The proposed method was validated with real water samples and satisfied spiked recoveries were achieved. All these results indicated that the proposed method was a low cost, easy to operate, efficient and sensitive method for the analysis of benzoylurea insecticides in water samples.

Amino acids are naturally occurring compounds in many edible or medicinal plants, which possess a variety of pharmacological effects on humans. The aim of this study is to develop and validate a hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method for absolute and relative quantification of amino acids without derivatization. The application of this method has been proven through 20 naturally occurring amino acids in 21 samples from different parts and phenological growth stage of S. alopecuroides. The method was performed on an ultra-high performance liquid chromatography separation system coupled with electrospray ionization mass spectrometry on a triple quadrupole mass spectrometer. The proposed absolute quantitative method was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery. The analysis results showed that S. alopecuroides is rich in free amino acids. In addition, relative quantitative determination of amino acids with several amino acids selected for the best accuracy was investigated. The accuracies of relative quantitative method for amino acids determinations suggest that it is feasible to quantify amino acids by the proposed relative quantitative determination method, which contribute to breaking through the choke point of lack of standards.

We describe the first application of a Quick, Easy, Cheap, Effective, Rugged and Safe extraction technique to the capillary zone electrophoresis analysis of monohydroxylated metabolites of polycyclic aromatic hydrocarbons in milk. Complete resolution of 2-hydroxyfluorenene, 1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyphenanthrene and 9-hydroxyphenanthrene was accomplished in 4 minutes of electrophoretic run. Limits of detection at the parts-per-billion were obtained with a single solvent (acetonitrile) for metabolite extraction and sample stacking. The small sample volume (1.2 milliliters) and the conservative usage of chemicals provided a simple and rapid procedure for the simultaneous extraction of numerous samples. Adding 4 minutes of electrophoretic run per sample, it should be possible to screen ten samples in approximately one hour of analysis time. The nanoliter extract volume required for sample injection allows for further chromatographic usage and confirmation of positive samples. The unique electrophoretic pattern of the studied metabolites demonstrates the potential for the unambiguous determination of positional isomers with very similar chromatographic behaviors and undistinguishable mass fragmentation patterns.

A rapid and convenient method was established to preparatively isolate the three ellagic acid types of compounds, which were the main polyphenols in Euphorbia pekinensis, by flexibly applying solvent extraction combined with counter-current chromatography. The total extract (extracted using 95% ethanol) of Euphorbia pekinensis was pretreated by two simple steps before counter-current chromatography isolation, following the procedure: the total extract was extracted by classical solvent extraction using petroleum ether and ethyl acetate, respectively, and then the ethyl acetate extract was suspended using 95% ethanol, after being allowed to stand overnight, the sediment was obtained. Partial sediment (100 mg) was then directly separated by counter-current chromatography with a two-phase solvent system composed of chloroform-95% ethanol-water-85% formic acid (50:50:50:5, v/v/v/v). About 22 mg of 3,3’-dimethoxy ellagic acid (1), 12 mg of 3,3′-di-O-methyl-4-O-(β-D-xylopyranosyl)ellagic acid (2), and 35 mg of ellagic acid (3) with purities of 96.0%, 95.2% and 95.4% were obtained respectively in one step separation within four hours. After being purified by washing with methanol, the purities of the three compounds obtained were all above 98%. The purities were determined by HPLC and their chemical structures were further identified by ¹H and ¹³C NMR. The recoveries were calculated as 84.6%, 85.7% and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for preparative separation of polyphenols from Euphorbia pekinensis.

Synthetic musks are organic compounds used as fragrance additives and fixative compounds in a diversity of personal care products. A new method based on QuEChERS extraction followed by gas chromatography-mass spectrometry for the analysis of twelve musks in personal care products was developed and validated. Some experimental parameters, such as total QuEChERS mass, sample mass: solvent volume ratio, type of extraction solvent, as well as salts and sorbents amount were investigated and optimised. The final method involves the musks extraction using acetonitrile, followed by the addition of anhydrous magnesium sulphate and sodium acetate. The clean-up step was performed using dispersive solid-phase extraction with primary and secondary amine and octadecyl-silica sorbents. This extraction procedure is fast (about 10 min) when compared to other traditional approaches. The method was robust for the matrices studied and shows a high precision (%RSD<15%) and accuracy (average recovery of 85%), allowing the detection of musks in minimum concentrations between 0.01 ng/g (galaxolide) and 15.80 ng/g (musk xylene). The developed method was applied to the analysis of twelve samples, which revealed musks concentrations ranging from 2 ng/g (toothpaste) to 882340 ng/g (perfumed body lotion).

The elution behavior of polyethylene and the three stereoisomers of polypropylene was studied on porous graphite along with three other carbon-based sorbents, carbon-clad zirconia particles, activated carbon and exfoliated graphite in a systematic way in this work. Decahydronaphthalene, 1,2,3,4-tetrahydrohaphthalene, 1,3,5-trimethylbenzene, xylene and p-xylene were used as mobile phases. While polyethylene is adsorbed to various extents on all the tested carbonaceous sorbents from the majority of the solvents, polypropylene is fully adsorbed only in selected cases. Testing alcohols (C7–C9) as mobile phase with Hypercarb™ indicates that all stereoisomers of polypropylene are selectively adsorbed and desorbed when a solvent gradient alcohol→1,2,4-trichlorobenzene is used at 160 °C. The retention of all stereoisomers of polypropylene increases with the polarity of the alcohol. Linear polyethylene is retained on Hypercarb™ even from 1,2-dichloro- and 1,2,4-trichlorobenzene, when a temperature below 120 °C is applied, while it is not retained from these solvents at higher temperatures. All stereoisomeric forms of polypropylene are not adsorbed under the same conditions. Some of the tested new sorbent-solvent systems have potential to be applied in routine analysis of industrially synthesised polyolefins.

The isoquinoline alkaloids are primary active ingredients of Corydalis, but analytical method for quality assessment of active ingredients in Corydalis impatiens (Pall.) Fisch hasn't been reported. A new, simple and multiple-components quantification method was developed for the simultaneous quantification of eleven isoquinoline alkaloids, including capnoidine, chelianthifoline, bicuculine, protopine, isoapocavidine, apocavidine, cavidine, tetrahydroepiberberine, ochotensimin, tetrahydrocoptisine and tetrahydrocorysamine in C. impatiens. Separation was performed on a reversed-phase C₁₈ column (150 mm× 4.6 mm, 5μm) with potassium dihydrogen phosphate buffer (pH2.5, adjusted by phosphoric acid) – acetonitrile (53:47, v/v) containing 0.3% sodium dodecyl sulfonate. The flow rate and detection wavelength were set at 1 mL/min and 295 nm, respectively. Full validation of the assay was carried out including linearity, precision, accuracy, stability, limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.999) in test range. The results demonstrated that the developed method was reliable, rapid and specific. The six batches of C. impatiens samples from different sources were determined using the established method. The contents of alkaloids ranged from 11.68 to 351.83μg/g. This method can be applied for quality evaluation and control of C. impatiens, eleven isoquinoline alkaloids were first reported on simultaneous determination with HPLC method.

Trends in Liquid Chromatography focuses on dedicated separation developments spanning different field of application ranging from sample preparation issues to miniaturization purposes. Chromatographic performances result from the porous media, its implantation inside “column” and its surface functionalization. Because molecular interactions govern chromatographic phenomena, surface functionalization is still a hot research topic. Besides standard approaches leading to surface functionalization, the use of new surface chemistry reactions opens new perspectives. Click chemistry belongs to this new class of chemical reactions, characterized by their specificity, compatibility with aqueous media and high reaction yields. In this frame, we review the use of click chemistry reactions in chromatographic sciences. In a first part, we present the click chemistry with a specific focus on its implementation in stationary phases. The use of these new clicked materials is detailed and discussed with respect to the chromatographic mode.

A broad forensic screening method for 256 analytes in whole blood based on a fully automated SPE robotic extraction and UHPLC-TOF-MS with data-independent acquisition has been developed. The limit of identification was evaluated for all 256 compounds and 95 of these compounds were validated with regard to matrix effects, extraction recovery, and process efficiency. The limit of identification ranged from 0.001 to 0.1 mg/kg, and the process efficiency exceeded 50% for 73 of the 95 analytes. As an example of application, 1335 forensic traffic cases were analyzed with the presented screening method. Of these, 992 cases (74%) were positive for one or more traffic relevant drugs above the Danish legal limits. Commonly abused drugs such as amphetamine, cocaine, and frequent types of benzodiazepines were the major findings. Nineteen less frequently encountered drugs were detected e.g., buprenorphine, butylone, cathine, fentanyl, LSD, mCPP, MDPV, mephedrone, 4-methylamphetamine, p-fluoroamphetamine, and PMMA. In conclusion, using UHPLC-TOF-MS screening with data-independent acquisition resulted in detection of common drugs of abuse as well as new designer-drugs and more rarely occurring drugs. Thus, TOF-MS screening of blood samples constitutes a practical way for screening traffic cases, with the exception of THC, which should be handled in a separate method.

Pre-column back-flushing is a matrix minimization technique in GC in which the carrier gas flow of the pre-column is reversed after the transfer of the highest boiling analyte to the analytical column. Practical details concerning this technology have rarely been published although it is widely used. This paper now-focuses on the practical implementation of pre-column back-flushing for pesticide residue analysis of complex food matrices. Fitting the analytical column into the pre-column was found to be essential for comparable analyte responses with and without back-flushing. The effectiveness of the reverse column flow technique is mainly affected by the transfer time after which back-flushing starts. The transfer time was found to depend on which kind of injected matrix is used and the state of the pre-column. For the regular adaptation of the transfer time in routine analysis, a simple test was introduced in which 13-C-labeled deltamethrin and indeno[1,2,3-c,d]pyrene were added to the prepared extract. Chromatograms, limits of quantification and relative standard deviations of up to 99 pesticides in citrus oil and liver extracts proved a clearer identification and enhanced quantification using pre-column back-flushing compared to measurements without this technology. Furthermore, reduced system maintenance could be achieved through back-flushing.

The ultrasound-enhanced in situ solvent formation microextraction was developed first time, and has been compared with the ultrasound-enhanced ionic liquid-assisted dispersive liquid-liquid microextraction for the high-performance liquid chromatographic analysis of acaricides in environmental water samples. The ionic liquid ([C₈MIM][PF₆]) was used as the green extraction solvent through two pathways . The experimental parameters, such as the type and volume of both the extraction solvent disperser solvent, ultrasonic time and salt addition, were investigated and optimized. The analytical performance using the optimized conditions proved the feasibility of the developed methods for the quantitation trace levels of acaricides by obtaining limits of detection ranged from 0.54 to 3.68 μg L⁻¹. The in situ solvent formation microextraction method possesses more positive characteristics than the ionic liquid-assisted dispersive liquid-liquid microextraction method (except for Spirodiclofen determination) when comparing the validation parameters. Both methods were successfully applied to determining acaricides in real water samples.

Supercritical fluid extraction (SFE) coupled with high-speed counter-current chromatography (HSCCC) was successfully used for the extraction and online isolation of the unstable compounds from plant Rosa damascene in a single extraction and separation operation via two stages. The solvent systems of SFE/HSCCC were optimized with the help of multi-exponential function model. At the first stage, the upper phase of the solvent system of n-butanol–MTBE–acetonitrile–0.1% aqueous TFA (1.7:1.0:0.8:4.0, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, and the target compounds were eluted with the corresponding lower phase to separate the hydrophobic compounds. At the second stage, the upper phase of the solvent system of n-hexane–ethyl acetate–methanol–water (3.2:1.0:2.8:2.6, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the moderate hydrophobic compounds. Six compounds including formononetin, delphinidin, cyaniding, 5,6,4′-trihydroxy-7,8-dimethoxy flavone, 5,3′-dihydroxy-7,8-dimethoxy flavone and 5-hydroxy-6,7,8,3′,4′-pentamethoxy flavone were successfully separated in one extraction–separation operation within 300 min. The targeted compounds were identified by MS and NMR. This research has opened up great prospects for industrial application of SFE/HSCCC to the extraction and separation of unstable compounds.

Columns for open tubular capillary electrochromatography, coated with a mixed-mode (reversed-phase/ion-exchange) stationary phase, were prepared by using the sol-gel method. The synthesizing procedure was optimized by changing the ratios of tetraethoxysilane, octyltriethoxysilane, and 3-aminopropyltriethoxysilane in the initial sol. Scanning electron microscopic studies reveal that a coating with about 400 nm thickness can be obtained. The inner surface properties of these capillaries were probed by measuring the electroosmotic flow as a function of pH. The surface of this stationary phase contains octyl, amine and residual silanol moieties; the amine and silanol groups determine the net charge on the inner surface of the capillary and can produce a switchable electroosmotic flow (anodal/cathodal). The performances of the columns were evaluated by open tubular capillary electrochromatography using a wide range of compounds (polycyclic aromatic hydrocarbons, aromatic acids, and aromatic amines).

A previous study has shown the possibility to identify methane using HeadSpace-Gas Chromatography / Mass Spectrometry and quantify it with a stable isotope as internal standard. The main drawback of the Gas Chromatography / Mass Spectrometry methods discussed in literature for methane measurement is the absence of a specific internal standard necessary to perform quantification. However, it becomes essential to develop a safer method to limit the manipulation of gaseous methane and to precisely control the injected amount of gas for spiking and calibration by comparison with external calibration. To avoid the manipulation of a stable isotope-labeled gas, we have chosen to generate an internal labeled standard gas in vial on the basis of the formation of methane by the reaction of Grignard reagent methylmagnesium chloride with deuterated water. This method allows precise measurement of methane concentrations in gaseous sample as well as in a solid or a liquid sample after a thermodesorption step in a HeadSpace vial. A full accuracy profile validation of this method is then presented.

Sample preparation is always the major bottleneck in analytical chemistry for the determination of pesticide residues. Different sample preparation methods have been proposed due to the wide variety of pesticides used and the inherent complexity of the matrices. In this study, different sample preparation methods including solid-phase extraction, matrix solid-phase dispersion, quick, easy, cheap, efficient, rugged and safe method and one-step completion method were compared and evaluated for extracting pesticides from lotus seeds. Analysis was carried out using gas chromatography-electron capture detector. The results showed that good recoveries for tested pesticides were obtained by using Florisil in the four methods, and the extraction efficiency of one-step completion method were superior to the other three methods. One-step completion method was confirmed to have good linearity, reproducibility, stability and recovery for the detection of 36 pesticides in lotus seed samples. The data collected from this study is expected to prove useful in regulating the concentration of the residues in lotus seeds, as well as in protecting the human health hazards posed by these residues.

We aim to determine the chemical constituents of three species of Cistanches Herba using high-performance liquid chromatography coupled with diode array detection and high-resolution mass spectrometry. Ten phenylethanoid glycosides were identified and further quantified as marker substances by high-performance liquid chromatography coupled with diode array detection method. The separation was performed on an Agilent TC-C18 column with 0.1% formic acid and methanol as the mobile phases under gradient elution. The analytical method was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery, and subsequently applied to evaluate the quality of 36 batches of Cistanche plants. The chemometric procedures (i.e., hierarchical clustering analysis and principal component analysis) were used to compare different species of Cistanches Herba, leading to successful classification of the Cistanche samples in accordance with their origins. In conclusion, this study provides a chemical basis for quality control of Cistanches Herba.

Benzotriazole ultra-violet stabilisers are emerging compounds used in personal care products and can enter surface water after passing through wastewater treatment plants without be removed. Because these analytes are strongly hydrophobic, there is an environmental risk of accumulation in solid matrices and magnification through the trophic chain. In this work, a method based on stir bar sorption extraction with liquid desorption is presented for the extraction of Benzotriazole ultra-violet stabilisers from water samples. Stir bar sorptive extraction was combined with ultra-high performance liquid chromatography with tandem mass spectrometry detection. All important factors affecting the stir bar sorptive extraction procedure are discussed, and the optimised method was applied to seawater and wastewater samples from Gran Canaria Island, providing good selectivity and sensitivity with limits of detection and limits of quantification in the range of 18.4–55.1 and 61.5–184 ng·L⁻¹, respectively. Recoveries between 68.4–92.2% were achieved for the more polar compounds, whereas the recoveries were lower for the two less polar compounds, most likely due to their strong absorption into the polydimethylsiloxane stir bar phase that does not allows the complete desorption. The repeatability studies gave relative standard deviations of between 6.45 and 12.6% for all compounds in the real samples.

Capillary electrophoresis was used for the first time to study the two-substrate enzyme glycerol kinase. The capillary was used as a nanoreactor in which the enzyme and its two substrates glycerol and adenosine 5’-triphosphate were in-capillary mixed to realize the enzymatic assay. For kinetic parameters determination, reactants were injected (50 mbar x 5 s) as follows: 1) incubation buffer; 2) adenosine 5’-triphosphate; 3) enzyme and 4) glycerol. Enzymatic reaction was then initiated by mixing the reactants using electrophoretically mediated microanalysis (+20 kV for 6 s) followed by a zero potential amplification step of 3 min. Finally, electrophoretic separation was performed; the product adenosine 5’-diphosphate was detected at 254 nm and quantified. For enzyme inhibition, the allosteric inhibitor fructose 1,6 -bisphosphate plug was injected before the first substrate plug and +20 kV for 8 s was applied for reactant mixing.

The present contribution is focused on the evaluation of a high-speed triple quadrupole mass spectrometer, carried out under moderately-fast gas chromatography conditions (analysis time: 16.6 minutes). The mass spectrometric instrument can be operated under high speed gas chromatography conditions, in both full-scan (maximum scan speed: 20,000 atomic mass units/second) and multiple reaction monitoring modes (minimum dwell time: 0.01 seconds). Additionally, the mass spectrometric system can generate full scan and multiple reaction monitoring information, simultaneously and rapidly.

In this work, Fe₂O₃ magnetic microspheres assisted microwave distillation and headspace single-drop microextraction were combined, and developed for determination of essential oil compounds in dried Zanthoxylum bungeanum Maxim. The Fe₂O₃ magnetic microspheres were used as microwave absorption solid medium for dry distillation of dried Zanthoxylum bungeanum Maxim. Using the proposed method, isolation, extraction and concentration of essential oil compounds can be carried out in a single step. The experimental parameters including extraction solvent, solvent volume, microwave power, irradiation time, and the amount of added Fe₂O₃ magnetic microspheres, were studied. The optimal analytical conditions were: 2.0μL decane as the extraction solvent, microwave power of 300W, irradiation time of 2 min, and the adding of 0.1 g Fe₂O₃ magnetic microspheres to Zanthoxylum bungeanum Maxim. The method precision was from 4% to 10%. A total of 52 compounds were identified by the proposed method. The conventional steam distillation method was also used for the analysis of essential oil in dried Zanthoxylum bungeanum Maxim and only 31 compounds were identified by steam distillation method. It was found that the proposed method is a simple, rapid, reliable, and solvent-free technique for the determination of volatile compounds in Chinese herbs.

A sensitive and selective confirmatory method for milk residue analysis of ten quinolones and eight cephalosporins by LC-MS/MS has been developed herein. For the chromatographic separation of target analytes, a Perfectsil ODS-2 (250 mm × 4 mm, 5 μm) analytical column was used and gradient elution was applied, using a mobile phase of 0.1% trifluoroacetic acid in water and 0.1% trifluoroacetic acid in acetonitrile.

This work concentrates on extending the utilization of multiple dual mode counter-current chromatography in chiral separations. Two aromatic acids, 2-(6-methoxy-2-naphthyl) propionic acid and 2-phenylpropionic acid, were enantioseparated by multiple dual mode counter-current chromatography using hydroxypropyl-β-cyclodextrin as chiral selector. The two-phase solvent systems consisting of n-hexane-ethyl acetate-0.1 mol L⁻¹ phosphate buffer pH2.67 containing 0.1 mol L⁻¹ hydroxypropyl-β-cyclodextrin (7.5:2.5:10 for 2-(6-methoxy-2-naphthyl) propionic acid and 7:3:10 for 2-phenylpropionic acid, v/v/v) were used. Conventional multiple dual mode and modified multiple dual mode were compared according to peak resolution under current separation mechanism. The influence of elution time after the first phase inversion and number of cycles for multiple dual mode were investigated. Peak resolution of 2-(6-methoxy-2-naphthyl) propionic acid and 2-phenylpropionic acid increased from 0.62 to 1.05 and 0.72 to 0.84 respectively using optimized multiple dual mode conditions. Being an alternative elution method for counter-current chromatography, multiple dual mode elution greatly improved peak resolution in chiral separations.

Eicosapentaenoic and docosahexaenoic acids are important bio-active fatty acids in fish oils. Monolithic HPLC columns both in the polymeric cation exchange (silver-ion) and reversed phase formats were compared with corresponding packed columns for the isolation of these acids from tuna oil ethyl esters. Monolithic columns in both formats enabled rapid (typically 5–10 min) separations compared with packed columns (30 min). Polymeric monolithic silver-ion disc column rapidly furnished mixtures of eicosapentaenoic and docosahexaenoic esters (90% purity) within 5–10 min, but was unable to resolve individual esters. A preparative version of the same column (80 mL bed volume) enabled isolation (> 88% purity) of 100 mg quantities of eicosapentaenoic and docosahexaenoic esters from esterified tuna oil within 6 min. Baseline separation of eicosapentaenoic and docosahexaenoic esters was achieved on all reversed phase columns. The results show that there is potential to use polymeric monolithic cation exchange columns for scaled-up preparation of eicosapentaenoic and docosahexaenoic ester concentrates from fish oils.

In this study, vinyl phenyl boronic acid modified lauryl methacrylate-based monolithic column was successfully prepared for cation exchange/hydrophobic interaction monolithic chromatography of small molecules and proteins in nano liquid chromatography. The polymeric mixture consisted of lauryl methacrylate, vinyl phenyl boronic acid as cation exchanger, ethylene dimethacrylate as cross-linker, polyethylene glycol and methanol as binary porogenic solvent and azobisisobutyronitrile as initiator. The resulting monolith showed good permeability and mechanical stability. Different ratios of monomer and porogens were used for optimizing the properties of the column. The monolithic column performance with respect to hydrophobic and cation exchange interactions was assesed by the separation a series of alkyl benzenes and anilines, respectively. Cis-diol containing compounds such as phenols were also utilized to evaluate the retention behaviours of the vinyl phenyl boronic acid modified monolithic column. The monolithic column showed cation exchange interactions in the separation of aniline compounds. Theoretical plate number up to 52 000 plates/m was successfully achieved. The prepared monolith was further applied to the proteins with different acetonitrile content.

In this work, for the first time, an ion imprinted polymer was developed for selective extraction and determination of gold ions. To increase the sorbent efficiency, this polymer was coated on a novel nanoporous carbon-based material, Carbohydrate-derived Max-Plank Gesellschoft 1, and it is also the first example of grafting imprinted polymer on nanoporous carbon material. These particles were applied successfully for preconcentration of ultra trace amount of gold ions with following determination by flame atomic absorption spectrometry. Some effective factors on the efficiency of gold ions extraction such as concentration and volume of eluent, sample and eluent flow rates and also effect of interfering ions especially palladium and platinum ions, were investigated. The limit of detection was determined to be 0.27 ng mL⁻¹. Furthermore, the precision of the method was calculated to be 2.14% under optimal conditions with recovery more than 97.3%. The technique was also used to determine the concentration of gold ions in mine stone samples with satisfactory results. The accuracy of this method was investigated by determination of gold ions concentrations in several reference materials with certified gold content.

Dispersive liquid-liquid microextraction method was developed for the determination of the amount of phthalate esters in bottled drinking water samples and dispersive liquid-liquid microextraction samples were analyzed by gas chromatography-mass spectrometry. Various experimental conditions influencing the extraction were optimized. Under the optimized conditions, very good linearity was observed for all analytes in a range between 0.05 and 150 μg L⁻¹ with coefficient of determination (R²) between (0.995–0.999). The limits of detection based signal to noise ratio of 3 were 0.005–0.22 μg L⁻¹. The reproducibility of dispersive liquid-liquid microextraction was evaluated. The relative standard deviations were 1.3–5.2% (n = 3). The concentrations of phthalates were determined in bottled samples available in half shell. To understand the leaching profile of these phthalates from bottled water, bottles were exposed to direct sunlight during summer (temperature from 34–57 ºC) and sampled at 12 hour intervals. Result showed that the proposed dispersive liquid-liquid microextraction is suitable for rapid determination of phthalates in bottled water and di-n-butyl, butyl benzyl and bis-2-ethylhexyl phthalates compounds leaching from bottles up to 36 hr. Thereafter, degradation of phthalates was observed.

This study investigates if deeper understanding is achieved when combining nonlinear and linear chromatographic column characterization methods. As test systems two hybrid columns (Phenomenex Gemini-NX C₁₈ and Kromasil Eternity C₁₈) and one classic one (Kromasil-C₁₈), were selected. The nonlinear methods were based on firm adsorption theory and involved determination of adsorption isotherms followed by calculations with a new numerical tool, adsorption energy distribution, on probe components at different pH values. The linear methods involved the hydrophobic subtraction model and selected probe components retention factors as a function of pH. The combined analysis indicated that both complementary and confirmative information can be achieved regarding the actual model systems.

Analysis of water soluble vitamins has been tremendously approached through the last decades. A multitude of HPLC methods have been reported with a variety of advantages/shortcomings, yet, the design space of HPLC analysis of these vitamins was not defined in any of these reports. As per the FDA, implementing the Quality by Design (QbD) approach for the analysis of commercially available mixtures is hypothesized to enhance the pharmaceutical industry via facilitating the process of analytical method development and approval. This work illustrates a multifactorial optimization of 3 measured plus 7 calculated influential HPLC parameters on the analysis of a mixture containing 7 common water soluble vitamins (B₁, B₂ B₆, B_12, C, PABA and PP). These 3 measured parameters are: gradient time, temperature and ternary eluent composition (B1:B2) and the seven calculated parameters are: flow rate, column-length, -ID, dwell volume, extra-column-volume,%B (start) and%B (end). The design is based on 12 experiments in which, examining of the multifactorial effects of these 3+7 parameters on the critical resolution and selectivity, was carried out by systematical variation of all these parameters simultaneously. The 12 basic runs were based on 2 different gradient time each at two different temperatures, repeated at 3 different ternary eluent compositions (methanol or acetonitrile or a mixture of both). Multi -dimensional robust regions of high critical R_s were defined and graphically verified. The optimum method was selected based on the best resolution separation in the shortest run time for a synthetic mixture, followed by application on two pharmaceutical preparations available in the market. The predicted retention times of all peaks were found to be in good match with the virtual ones. In conclusion, the presented report offers an accurate determination of the Design Space for critical resolution in the analysis of water soluble vitamins by HPLC, which would help the regulatory authorities to judge the validity of presented analytical methods for approval.

In this study, a hollow fiber-assisted liquid-phase microextraction technique coupled with liquid chromatography-tandem mass spectrometry is described to detect avermectins (abamectin, ivermectin, moxidectin, and doramectin) in stream water. A Accurel polypropylene membrane was used as the hollow fiber, and dihexyl ether was used as the extraction solvent. The optimal extraction conditions for hollow fiber-assisted liquid-phase microextraction were a 4 cm fiber length, 45 min extraction time, 200 rpm, and 1 min desorption time with methanol as the desorption solvent. The linear range was 0.15–100 ng·mL⁻¹ (r² = 0.994–0.998), and the limits of detection and quantification were 0.15 and 0.5 ng·mL⁻¹, respectively. Recovery rates were determined at 1, 5, and 10 ng·mL⁻¹, and the results were in the range of 80.1 to 93.7%. The intra-day and inter-day repeatability ranged from 2.8 to 8.0% and from 6.1 to 13.3%, respectively. The hollow fiber-assisted liquid-phase microextraction method developed was applied to detect avermectins in stream water samples collected from 14 different sites near livestock farms located in Honam area, Republic of Korea; however, none of the samples contained avermectin residues. Hollow fiber-assisted liquid-phase microextraction combined with a liquid chromatography-tandem mass spectrometry method was successfully applied for an environmentally friendly identification of avermectins in water samples. Hollow fiber-assisted liquid-phase microextraction represents an attractive approach for conventional liquid-liquid extraction.

Ginkgo biloba leaf extract has been widely used in dietary supplements and more recently in some foods and beverages. In addition to the well-known flavonol glycosides and terpene lactones, G. biloba leaves are also rich in amino acids. To determine the content of free amino acids, a reliable method has been established by using hydrophilic interaction ultra-high performance liquid chromatography coupled with electrospray ionization mass. 20 free amino acids were simultaneously determined without derivatization in 12 min. The proposed method was fully validated in terms of linearity, sensitivity, repeatability as well as recovery. Furthermore, the principal component analysis was applied to different G. biloba leaves collected in November (after fruit harvest season), which revealed that the samples from different production areas exhibited regional disparity in different clusters in accordance with their various hydrophilic interaction liquid chromatography coupled with mass profiles. The established approach could be helpful for evaluation of the potential values as dietary supplements and the quality control of G. biloba leaves, which might also be utilized for the investigation of other medicinal herbs containing amino acids.

Electrokinetic supercharging is one of the most powerful sample-stacking methods that combines field amplified sample injection and transient ITP. In counter-flow electrokinetic supercharging, a constant counter pressure is applied during sample injection in order to counterbalance the movement of the injected sample zone. As a result, there will be a pronounced increase in the amount of sample injected and the portion of the capillary available for electrophoresis. In this report, counter-flow electrokinetic supercharging optimization factors such as the electric field application in the constant voltage and constant current modes, the magnitude of counter pressure, and the terminating electrolyte concentrations were investigated. The enrichments obtained with a 30 min injection of 10 nM catecholamines in 5 mM terminating electrolyte solution in the constant voltage mode applying a counter pressure of 1.3 psi were 41000-fold for dopamine, 50 000-fold for norepinephrine, and 32 000-fold for epinephrine, yielding detection limits of 1.3, 1.4, and 1.2 nM, respectively, with absorbance detection at 200 nm.

An efficient separation process of flavonoid from Taxus wallichiana var. mairei remainder extracts free of taxoids was developed in this study. AB-8 macroporous resin and polyamide resin offered the fine adsorption capacity, and its adsorption rate at 30°C fitted well to the Langmuir and Freundich isotherms. Resin dynamic adsorption and desorption experiments were conducted to optimize the separation process of total flavonoids from T. wallichiana var. mairei remainder extracts free of taxoids. The optimum parameters for adsorption by AB-8 resin were as follows: (1) the concentration of flavonoids in a sample solution of 5.61 mg/mL with a processing volume of 2 bed volume (BV) (60 mL); (2) for desorption, ethanol–water (80:20, v/v), with 6 BV as an eluent at a flow rate of 2 BV/h. After a one-run treatment with AB-8 resin, the content of flavonoids was increased 5.10-fold from 4.05 to 20.65%. The optimum parameters for adsorption by polyamide resin were as follows: processing volume of 2 BV (30 mL); for desorption, ethanol–water (70:30, v/v), with 8 BV as an eluent at a flow rate of 2 BV/h. After one-run treatment with polyamide resin, the content of total flavonoids increased from 20.65 to 65.21%. The method will provide a potential approach for large-scale separation and purification of flavonoid for its wide pharmaceutical use.

In the present study, we report a new method for the determination of two primary thiols, cysteine (CYS) and glutathione (GSH), by hydrophilic interaction LC. The polar analytes are separated isocratically using a mobile phase consisting of 65% acetonitrile/35% ammonium acetate (15 mmol/L, pH 2.0) and are detected at 285 nm following on-line postcolumn derivatization by the thiol-selective reagent methyl propiolate. The main figures of merit included linearity in the range of 5–200 μmol/L and an LOD 0.6 μmol/L for both compounds. The absence of matrix effect allowed the determination of CYS and GSH in various yeast samples. GSH was present in most of the samples at levels ranging between 0.9 and 3.1 mg/g, whereas CYS was determined in only one sample at a significantly lower concentration. In terms of accuracy, the percent recoveries ranged between 91.2 and 105.6% for GSH, and 91.6 and 106.9% for CYS.

Reproducible fabrication of the hierarchically porous monolithic silica in a large volume exceeding 1000 mL has been established. By the hydrothermal enlargement of the fully accessible small pores to exceed 50 nm in diameter, the capillary force emerged on solvent evaporation was dramatically reduced, which allowed the preparation of crack-free monoliths with evaporative solvent removal under an ambient pressure. The local temperature inhomogeneity within a reaction vessel in a large volume was precisely controlled to cancel the heat evolved by the hydrolysis reaction of tetramethoxysilane and that consumed to melt ice cubes dispersed in the solution, resulting in large monolithic silica pieces with improved structural homogeneity. Homogeneity of the pore structure was confirmed, both on macro- and mesoscales, using SEM, mercury intrusion, and nitrogen adsorption/desorption measurements. Furthermore, the deviations in chromatographic performance were examined by evaluating multiple smaller monolithic columns prepared from the monolithic silica pieces cut from different parts of a large monolith. All the daughter columns thus prepared exhibited comparable performances to each other to prove the overall homogeneity of the mother monolith. Preliminary results on high-speed separation of peptides and proteins by the octadecylsilylated silica monolith of the above production have also been demonstrated.

A method of simultaneous separation of water- and fat-soluble vitamins using pressure-assisted CEC with a methacrylate-based capillary monolithic column was developed. In the proposed method, water-soluble vitamins were mainly separated electrophoretically, while fat soluble-ones were separated chromatographically by the interaction with a methacrylate-based monolith. A mixture of six water-soluble and four fat-soluble vitamins was separated simultaneously within 20 min with an isocratic elution using 1 M formic acid (pH 1.9)/acetonitrile (30:70, v/v) containing 10 mM ammonium formate as a mobile phase. When the method was applied to a commercial multivitamin tablet and a spiked one, the vitamins were successfully analyzed, and no influence of the matrix contained in the tablet was observed.

In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water.

The purpose of applying a countercurrent flow to isotachophoretic migration is to increase the effective separation channel length during ITP. However, severe dispersion induced by applying a counterflow can be detrimental to ITP. This paper uses numerical simulations in a 2D axisymmetric domain to investigate the dispersion caused by a parabolic counterflow in open-capillary ITP. Counterflow in these simulations was generated by applying a back pressure to stop the isotachophoretic stack, i.e., forming stationary ITP zones. It is found that dispersion is strongly related to analyte molecular diffusivity: R-phycoerythrin, due to its small diffusivity, showed ∼20-fold increase in zone width in stationary counterflow ITP, compared to ITP in the absence of counterflow, while fluorescein only had ∼10% increase in zone width under similar operating conditions. Applying the Taylor–Aris dispersion formula in counterflow ITP simulations provided only a rough estimate of the dispersion, e.g., overestimation of analyte zone widths. Experiments on counterflow ITP were conducted in a silica capillary that was covalently and dynamically coated to exclude electroosmosis effect. The counterflow was generated by adjusting the relative height of the fluids in the two reservoirs at the capillary ends. Good qualitative agreement between simulations and experiments was found.

We developed and validated an accurate and sensitive LC–MS/MS method for the simultaneous quantitation of ginsenoside Rg3 and Rh2 epimers (R-Rg3, S-Rg3, R-Rh2, and S-Rh2) in rat plasma. Analytes were extracted from 0.1 mL aliquots of rat plasma by liquid–liquid extraction, using 2 mL of ethyl acetate. In this assay, dioscin (500 ng/mL) was used as an internal standard. Chromatographic separation was conducted using an Acclaim RSLC C₁₈ column (150 × 2.1 mm, 2.2 μm) at 40°C, with a gradient mobile phase consisting of 0.1% formic acid in distilled water and in acetonitrile, a flow rate of 0.35 mL/min, and a total run time of 20 min. Detection and quantification were performed using a mass spectrometer in selected reaction-monitoring mode with negative electrospray ionization at m/z 783.4 → 161.1 for R-Rg3 and S-Rg3, m/z 621.3 → 161.1 for R-Rh2 and S-Rh2, and m/z 867.2 → 761.5 for the internal standard. For R-Rg3 and S-Rg3, the lower limit of quantification was 5 ng/mL, with a linear range up to 500 ng/mL; for R-Rh2 and S-Rh2, the lower limit of quantification was 150 ng/mL, with a linear range up to 6000 ng/mL. The coefficient of variation for assay precision was less than 10.5%, with an accuracy of 86.4–112%. No relevant cross-talk or matrix effect was observed. The method was successfully applied to a pharmacokinetic study after oral administration of 400 mg/kg and 2000 mg/kg of BST204, a fermented ginseng extract, to rats. We found that the S epimers exhibited significantly higher plasma concentrations and area under curve values for both Rg3 and Rh2. This is the first report on the separation and simultaneous quantification of R-Rg3, S-Rg3, R-Rh2, and S-Rh2 in rat plasma by LC-MS/MS. The method should be useful in the clinical use of ginseng or its derivatives.

A mathematical model is constructed and solved that could describe the dynamic behavior of the adsorption of a solute of interest in single and stratified columns packed with partially fractal porous adsorbent particles. The results show that a stratified column bed whose length is the same as that of a single column bed, provides larger breakthrough times and a higher dynamic utilization of the adsorptive capacity of the particles than those obtained from the single column bed, and the superior performance of the stratified bed becomes especially more important when the superficial velocity of the flowing fluid stream in the column is increased to accommodate increases in the system throughput. This occurs because the stratified column bed provides larger average external and intraparticle mass transfer and adsorption rates per unit length of packed column. It is also shown that increases in the total number of recursions of the fractal and the ratio of the radii between larger and smaller microspheres that make up the partially fractal particles, increase the intraparticle mass transfer and adsorption rates and lead to larger breakthrough times and dynamic utilization of the adsorptive capacity of the particles. The results of this work indicate that highly efficient adsorption separations could be realized through the use of a stratified column comprised from a practically reasonable number of sections packed with partially fractal porous adsorbent particles having reasonably large (i) total number of recursions of the fractal and (ii) ratio of the radii between larger and smaller microspheres from which the partially fractal particles are made from. It is important to mention here that the physical concepts and modeling approaches presented in this work could be, after a few modifications of the model, applied in studying the dynamic behavior of chemical catalysis and biocatalysis in reactor beds packed with partially fractal porous catalyst particles.

A rapid analytical method based on rapid resolution LC coupled with MS/MS was first established to quantify seven alkaloids in processed Fuzi decoction. The chromatographic method was optimized to allow simultaneous analysis of all analytes in 5 min and demonstrated good linearity (r > 0.9995), repeatability (RSD < 4.36%), intra- and interday precisions (RSD < 5.07%) with good accuracies (97.76–105.08%) and good recovery (95.0–107.5%) of seven alkaloids, namely higenamine, benzoylhypaconine, benzoylmesaconine, benzoylaconine, aconitine, hypaconitine, and mesaconitine. The LODs for these markers were in the range of 2.30–17.00 pg/mL. Quantitative analysis of the seven alkaloids in Baifupian decoction and Heishunpian decoction showed that the content of the seven marker chemicals varied significantly and concluded that the quality of Fuzi was greatly affected by different processed methods. The developed method could be used as a rapid, sensitive, and reliable approach for assessment of the quality of processed Fuzi and related decoction.

Yunnan Baiyao is a widely used herbal prescription in traditional medicine for the treatment of bleeding and hematological diseases, while its chemical profile remains elusive. In this work, a novel methodology combining polarity-directed extraction technique with a diagnostic ion filtering strategy based on LC hybrid ion trap TOF-MS analysis was developed for global, efficient, and rapid characterization of components in Yunnan Baiyao. Di-ethyl ether, n-butanol, and ethanol/water (70:30, v/v) covering low-to-high polarity ranges were chosen as the extraction solvent, respectively. The results clearly showed that, compared with conventional single extraction solvent, collaboratively using extraction solvents with different polarities can effectively increase the number of detected peaks and enrich the product ions information in multistage mass spectra analysis. By further matching diagnostic ions and fragmental pathways, a total of 34 components were successfully identified. Our work clearly demonstrates that integrating polarity-directed extraction and diagnostic ion filtering techniques is a powerful and reliable strategy for global detection and identification of complex chemicalome from herbal prescriptions, and may open new avenues for chemical analysis in other complex mixtures.

Magnetic bead cellulose activated with divinyl sulfone was used for the immobilization of Staphylococcus aureus endoproteinase Glu-C (EC 3.4.21.19). The immobilized proteinase was characterized by increased thermostability, by decreased self-cleavage activity, and a possibility of repeated use. The prepared immobilized enzyme was applied for the proteolytic cleavage of α-casein and BSA under different conditions (different composition of buffers, different pH, and different time of digestion). The possibilities of the direct use of enzyme reaction products for MALDI TOF MS analysis were shown.

A variety of related impurities, including starting materials, process impurities, and degradation products, can be detected in propofol. In this article, a sensitive and selective GC-MS/MS method using pulsed splitless injection technique for the determination of 11 main related impurities in propofol in one chromatogram is investigated. This method is extensively validated for its linearity, recovery, precision, LOD, and LOQ, and is able to detect trace-level related impurities (LOD = 0.2–5.6 μg/g) in propofol bulk drug. Stressed tests proposed that oxidative degradation, photolytic degradation, and heat are the main causes for the formation of degradation products in propofol.

A novel bromoquinolinium reagent, i.e. 1-(3-aminopropyl)-3-bromoquinolinium bromide (APBQ), was synthesized for the analysis of carboxylic acids. A simple and practical precolumn derivatization procedure using the APBQ in RP chromatography and MS (HPLC-MS) has been developed using bile acids and free fatty acids, as the representative carboxylic acids in biological samples. The APBQ efficiently reacted with carboxylic acids at 60°C for 60 min in the presence of N,N-dicyclohexylcarbodiimide and pyridine as the activation reagents. Because the APBQ possesses a bromine atom in the structure, the identification of a series of carboxylic acids was easily achieved due to the characteristic bromine isotope pattern in the mass spectra. The APBQ also has a quaternary amine structure, thus the positively charged derivatives are predominate for the highly sensitive detection of carboxylic acids. The APBQ was successfully applied to the selective determination of biological carboxylic acids in human plasma. The bile acids (chenodeoxycholic acid and deoxycholic acid) and several saturated (stearic acid and palmitic acid) and unsaturated free fatty acids (oleic acid and linoleic acid) were reasonably determined by HPLC-MS under the proposed procedure. Based on the results of analyses of human plasma and saliva, the proposed procedure using APBQ seems to be applicable for the qualitative and quantitative analyses of a series of carboxylic acids in biological samples.

Four flavonoids, isoastilbin, astilbin, isoengelitin, and engelitin were isolated and purified simultaneously from Smilacis Glabrae Roxb. for the first time by high performance counter-current chromatography using a system consisting of n-hexane–n-butanol–water (1:2:3, v/v/v). A total of 392.6 mg of astilbin, 71.4 mg of isoastilbin, 47.4 mg of engelitin, and 10.3 mg of isoengelitin were purified from 1.89 g of the ethyl acetate extract of Smilacis Glabrae Roxb. in six runs, each at over 94.51% purity as determined by HPLC. The structures of the four compounds were identified by their retention time, the LC-ESI-MSⁿ in the negative ion mode, and confirmed by ¹H-NMR experiments. The characteristic LC-ESI-MS fragmentation patterns of the four compounds were discussed.

In the present study, we propose the first HPLC method coupled to postcolumn derivatization for the determination of rimantadine in human urine samples. The analyte and amantadine (internal standard) were isocratically separated using an RP monolithic stationary phase (100 × 4.6 mm id) with a mobile phase consisting of CH₃OH/phosphate buffer (25 mmol/L, pH 3.0) at a volume ratio of 50:50. Postcolumn derivatization involved on-line reaction with o-phthalaldehyde (20 mmol/L) and N-acetyl-cysteine (5 mmol/L) at alkaline medium (100 mmol/L borate pH 11.0). Spectrofluorimetric detection at λ_ex/λ_em = 340/455 nm enabled the selective and sensitive determination of rimantadine in urine samples at a range of 50–500 ng/mL with an LOD of 5 ng/mL. Human urine samples were analyzed successfully after SPE using hydrophilic-lipophilic balanced RP cartridges (30 mg/mL, Oasis HLB). Recoveries ranged between 89.7 and 102.7%.

Despite of membrane catechol-O-methyltransferase (MBCOMT, EC 2.1.1.6) physiological importance on catecholamines’ O-methylation, no studies allowed their total isolation. Therefore, for the first time, we compare the performance of three hydrophobic adsorbents (butyl-, epoxy-, and octyl-Sepharose) in purification of recombinant human COMT (hMBCOMT) from crude Brevibacillus choshinensis cell lysates to develop a sustainable chromatographic process. Hydrophobic matrices were evaluated in terms of selectivity and hMBCOMT's binding and elution conditions. Results show that hMBCOMT's adsorption was promoted on octyl and butyl at ≤375 mM NaH₂PO_4, while on epoxy higher concentrations (>850 mM) were required. Additionally, hMBCOMT's elution was promoted on epoxy, butyl, and octyl using respectively 0.1–0.5, 0.25–1, and 1% of Triton X-100. On butyl media, a stepwise strategy using 375 and 0 mM NaH₂PO₄, followed by three elution steps at 0.25, 0.7 and 1% Triton X-100, allowed selective hMBCOMT isolation. In conclusion, significant amounts of MBCOMT were purified with high selectivity on a single chromatography procedure, despite its elution occurs on multiple peaks. Although successful applications of hydrophobic interaction chromatography in purification of membrane proteins are uncommon, we proved that traditional hydrophobic matrices can open a promising unexplored field to fulfill specific requirements for kinetic and pharmacological trials.

Cyclofructan-based chiral stationary phases were previously shown as a promising possibility for separation of chiral compounds in high performance liquid chromatography. In this work retention and enantiodiscrimination properties of the 3,5-dimethylphenyl carbamate cyclofructan 7 chiral stationary phase are described in supercritical fluid chromatography. The results obtained in both of the separation methods were compared. A set of compounds with axial or central chirality was used as analytes. The effect of mobile phase composition, that is, addition of different alcohol modifiers and/or trifluoroacetic acid to carbon dioxide, was examined in the supercritical system. Similarly, mobile phases composed of hexane modified with propan-2-ol and/or trifluoracetic acid were used in liquid chromatography. A linear free energy relationship model was utilized for characterization of interactions that are decisive for retention and separation in both techniques. Dispersion interactions showed similar negative values using both methods. The main contribution of hydrogen bond acidity was also comparable for both methods. The propensity to interact with n- and/or π-electron pairs of solutes was significant only in the supercritical system.

Venlafaxine is used for the treatment of major depression and generalized anxiety disorders. Because its active metabolite, O-desmethylvenlafaxine, has also a similar activity, the purpose of this work was to develop a simple method for simultaneous quantitation of both drugs using HPLC with UV detection. The saliva was chosen as diagnostic material because of its easy accessibility and possibility of sampling by patients, for example, at home. The sample pretreatment by liquid–liquid extraction allows to separate both compounds from this diagnostic material with a high recovery, varying between 92.65 and 104.78%. The major advantage of the validated method lies in its sensitivity, reproducibility, and specificity for routine quantitation of the venlafaxine and O-desmethylvenlafaxine in the human saliva. The low detection and quantification values (2.8–3.1 and 9.4–10.2 ng/mL, respectively) enable to quantify both species excreted with saliva at the nanogram level. The applicability of the method was verified by analysis of the saliva obtained from depressed women treated with venlafaxine. The results suggest that the method could be used for therapeutic drug monitoring in patients undergoing treatment with venlafaxine, especially when metabolic anomalies or low compliance are suspected, or in the case of polypharmacy.

The present work illustrates potentialities of CE hyphenated with MS/MS for the simultaneous determination and identification of a mixture of simultaneously acting drugs in pharmaceutical and biological matrices. Here, the hyphenation was provided by ESI interface, while the MS/MS technique was based on the triple quadrupole configuration. Three drugs, namely pheniramine, phenylephrine, and paracetamol were determined and identified with high reliability due to their characterization in three different dimensions, i.e. electrophoresis and MS/MS, that prevented practically any interference. Appropriately selected transitions of the analytes (parent ion-quantifier product ion-qualifier product ion) provided their selective determination at maximum S/N. The proposed CE-MS/MS method was validated (LOD/LOQ, linearity, precision, recovery, accuracy) and applied for (i) the multidrug composition pharmaceuticals, namely Theraflu®, and (ii) human urine taken after per-oral administration of the same pharmaceutical preparation. The method was applied also for the investigation of potential weak associates of the drugs and monitoring of predicted (bio)degradation products of the drugs. Successful validation and application of the proposed method suggest its routine use in highly effective and reliable advanced drug control and biomedical research.

Caffeine test solute was employed in combination with an internal standard (IS), 1,4-dimethoxybenzene, in preparative-gas chromatography (prep-GC), with nuclear magnetic resonance (NMR) experiments. The IS served to: (i) quantify the trapping efficiency of an external trapping assembly, consisting of a capillary column cryotrap at the end of the analytical column; (ii) quantify the solute response in different NMR samples; and (iii) permit correlation of expected level of response of a compound in the NMR experiment, based on relative responses of the IS and solute in the GC result. The recovery rate of caffeine from multiple injections of sample (1×, 2×, 5× and 10×) was 69.6 ± 1.3%, which correlated well (R² = 0.999) with the number of injections of compound. The ¹H-NMR spectrum was sufficient to enable structural characterisation of the reference caffeine compound, and was achieved with recovery of amounts of ≤10 μg from a single aliquot. Less than 400 μg of collected caffeine (40 replicate injections) was sufficient for structural characterisation by ¹³C-NMR spectral analysis. The method allows development of approaches to separate unknown compounds in complex samples, and to separately use MS and NMR for their characterisation.

Metal deactivator additives (MDAs) have been used for over 60 years to prevent metal catalyzed reactions in petroleum products; a commonly used metal deactivator is N,N′-disalicylidene-1,2-propanediamine. The quantitation of low MDA concentrations in fuels is challenging due to the complexity of the sample matrix. In this work, this difficulty was overcome using GC × GC hyphenated with a nitrogen chemiluminescence detector. The high resolution power of GC × GC avoided co-elution between the MDA and other sample matrix compounds; while the enhanced sensitivity of GC × GC and the use of a nitrogen chemiluminescence detector supplied a high sensitivity and specificity for nitrogen compounds. For the analysis, the MDA additive was derivatized with the silylation agent N,O-bis (trimethylsilyl)trifluoroacetamide at room temperature and its quantitation was based on an external calibration curve; good linear response was obtained in the 1.4–8.6 ppm range.

A new reversed phase ultra performance liquid chromatography coupled with evaporative light scattering detection is developed for the fast and direct quantification of underivatized muscone in precious herbal medicine musk. Separation of muscone was achieved on a Waters Acquity BEH C₁₈ (50 × 2.1 mm id, 1.7 μm) column. The runtime was as short as 5 min. The mode of evaporative light scattering detection was set at Impact On. The influence of evaporative light scattering detection condition on sensitivity was investigated. The optimized condition was: drift tube temperature at 30°C, gas flow rate 4.2 L/min. The method was validated with respect to the precision, sensitivity, accuracy, linearity, stability, and robustness were measured in this paper. The calibration curves showed good linear regression (r = 0.9914) within the test range. The recovery rate was 98.6%. The limit of detection for muscone was 2.0 ng. The validated method was rapid, simple, reproducible, and convenient for the quantification of muscone in musk and the related products.

A simple, rapid, and sensitive method based on dispersive liquid–liquid microextraction combined with HPLC-UV detection applied for the quantification of chlordiazepoxide in some real samples. The effect of different extraction conditions on the extraction efficiency of the chlordiazepoxide drug was investigated and optimized using central composite design as a conventional efficient tool. Optimum extraction condition values of variables were set as 210 μL chloroform, 1.8 mL methanol, 1.0 min extraction time, 5.0 min centrifugation at 5000 rpm min⁻¹, neutral pH, 7.0% w/v NaCl. The separation was reached in less than 8.0 min using a C₁₈ column using isocratic binary mobile phase (acetonitrile/water (60:40, v/v)) with flow rate of 1.0 mL min⁻¹. The linear response (r² > 0.998) was achieved in the range of 0.005–10 μg mL⁻¹ with detection limit 0.0005 μg mL⁻¹. The applicability of this method for simultaneous extraction and determination of chlordiazepoxide in four different matrices (water, urine, plasma, and chlordiazepoxide tablet) were investigated using standard addition method. Average recoveries at two spiking levels were over the range of 91.3–102.5% with RSD < 5.0% (n = 3). The obtained results show that dispersive liquid–liquid microextraction combined with HPLC-UV is a fast and simple method for the determination of chlordiazepoxide in real samples.

Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene-based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π–π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC-MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84–13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene-based SPE disk in environmental analytical.

A case study is presented for the forensic identification of several spilled biodiesels and its blends with petroleum oil using integrated forensic oil fingerprinting techniques. The integrated fingerprinting techniques combined SPE with GC/MS for obtaining individual petroleum hydrocarbons (aliphatic hydrocarbons, polyaromatic hydrocarbons and their alkylated derivatives and biomarkers), and biodiesel hydrocarbons (fatty acid methyl esters, free fatty acids, glycerol, monoacylglycerides, and free sterols). HPLC equipped with evaporative scattering laser detector was also used for identifying the compounds that conventional GC/MS could not finish. The three environmental samples (E1, E2, and E3) and one suspected source sample (S2) were dominant with vegetable oil with high acid values and low concentration of fatty acid methyl ester. The suspected source sample S2 was responsible for the three spilled samples although E1 was slightly contaminated by petroleum oil with light hydrocarbons. The suspected source sample S1 exhibited with the high content of glycerol, low content of glycerides, and high polarity, indicating its difference from the other samples. These samples may be the separated byproducts in producing biodiesel. Canola oil source is the most possible feedstock for the three environmental samples and the suspected source sample S2.

A simple, sensitive and low-cost method using CE coupled with glucose-β-CD interaction assisted ACN stacking technique has been developed for quantification of trace amlodipine in dog plasma. The plasma samples were extracted with methyl tert-butyl ether. The separation was performed at 25°C in a 31.2 cm × 75 μm fused-silica capillary with an applied voltage of 15 kV. The BGE was composed of 6.25 mM borate/25 mM phosphate (pH 2.5) and 5 mg/mL glucose-β-CD. The detection wavelength was 200 nm. Because CD could diminish the interaction between drugs and matrix, and derivation groups of CD play an important role in separation performance, the effects of β-CD, and its derivatives on the separation were studied at several concentrations (0, 2.5, 5.0, 10.0 mg/mL). In this study, organic solvent field-amplified sample stacking technique in combination with glucose-β-CD enhanced the sensitivity about 60–70 folds and glucose-β-CD could effectively improve the peak shape. All the validation data, such as accuracy, precision extraction recovery, and stability, were within the required limits. The calibration curve was linear for amlodipine from 1 to 200 ng/mL. The method developed was successfully applied to the pharmacokinetic studies of amlodipine besylate in beagle dogs.

In this study, a rapid and sensitive analytical method for the determination of methyl-, ethyl-, propyl-, and butyl esters of para-hydroxy benzoic acid (parabens) in personal care products was developed and fully validated. Test portions were extracted with methanol followed by vortexing, sonication, centrifugation, and filtration without derivatization. The four parabens were quantified by GC-MS/MS in the electron ionization mode. Four corresponding isotopically labeled parabens were selected as internal standards, which were added at the beginning of the sample preparation and used to correct for recovery and matrix effects. Sensitivity, extraction efficiency, and recovery of the respective analytes were evaluated. The coefficients of determination (r²) were all greater than 0.995 for the four parabens investigated. The recoveries ranged from 97 to 107% at three spiked levels and a one-time (single) extraction efficiency greater than 97% was obtained. This method has been applied to screen 26 personal care products. This is the first time that a unique GC-MS/MS method with dynamic selected reaction monitoring and confirmation of analytes has been used to determine these parabens in cosmetic personal care products.

A novel, sensitive, and reliable LC-MS/MS method for multiresidue analysis of nine β-agonists (salbutamol, terbutaline, cimaterol, fenoterol, clorprenaline, ractopamine, tulobuterol, clenbuterol, and penbuterol) in four farm animal muscles was developed. Muscle matrix was extracted with acetonitrile–10% sodium carbonate solution, and then was subjected to cleanup using a SPE cartridge packed with new polymer synthesized in acetone. Chromatographic separation of the components was performed on a Luna C₁₈ column using 0.1% of formic acid in water and acetonitrile. The mass spectrometer was operated in the positive electrospray mode. Good precision and accuracy were obtained for all analytes (except for fenoterol) at the spiked three levels of 1.0, 10, and 50 μg/kg. The decision limit and detection capability of nine β-agonists ranged from 0.04 to 0.18 and 0.15 to 0.69 μg/kg, respectively. The method developed was successfully applied to the monitoring of nine β-agonists in pork, beef, mutton, and chicken from Chinese markets.

An activity-based approach to optimize the ultrasonic-assisted extraction of antioxidants from Pericarpium Citri Reticulatae (Chenpi in Chinese) was developed. Response surface optimization based on a quantitative composition-activity relationship model showed the relationships among product chemical composition, antioxidant activity of extract, and parameters of extraction process. Three parameters of ultrasonic-assisted extraction, including the ethanol/water ratio, Chenpi amount, and alkaline amount, were investigated to give optimum extraction conditions for antioxidants of Chenpi: ethanol/water 70:30 v/v, Chenpi amount of 10 g, and alkaline amount of 28 mg. The experimental antioxidant yield under the optimum conditions was found to be 196.5 mg/g Chenpi, and the antioxidant activity was 2023.8 μmol Trolox equivalents/g of the Chenpi powder. The results agreed well with the second-order polynomial regression model. This presented approach promised great application potentials in both food and pharmaceutical industries.

A simple, rapid, and highly sensitive method for simultaneous analysis of anti-inflammatory drugs (naproxen, ibuprofen, and mefenamic acid) in diluted human serum was developed using the electrochemically controlled solid-phase microextraction coupled to ion mobility spectrometry. A conducting molecularly imprinted polymer film based on polypyrrole was synthesized for the selective uptake and release of drugs. The film was prepared by incorporation of a template molecule (naproxen) during the electropolymerization of pyrrole onto a platinum electrode using cyclic voltammetry method. The measured ion mobility spectrometry intensity was related to the concentration of analytes taken up into the films. The calibration graphs (naproxen, ibuprofen, and mefenamic acid) were linear in the range of 0.1–30 ng/mL and detection limits were 0.07–0.37 ng/mL and relative standard deviation was lower than 6%. On the basis of the results obtained in this work, the conducting molecularly imprinted polymer films as absorbent have been applied in the electrochemically controlled solid-phase microextraction and ion mobility spectrometry system for the selective clean-up and quantification of trace amounts of anti-inflammatory drugs in human serum samples. Scanning electron microscopy has confirmed the nano-structure morphology of the polypyrrole film.

Short-chain fatty acids are the major end products of bacterial metabolism in the large bowel. They derive mostly from the bacterial breakdown of carbohydrates and are known to have positive health benefits. Due to the biological relevance of these compounds it is important to develop efficient, cheap, fast, and sensitive analytical methods that enable the identification and quantification of the short-chain fatty acids in a large number of biological samples. In this study, a gas chromatography-mass spectrometry method was developed and validated for the analysis of short-chain fatty acids in faecal samples. These volatile compounds were extracted with ethyl acetate and 4-methyl valeric acid was used as an internal standard. No further cleanup, concentration, and derivatization steps were needed and the extract was directly injected onto the column. Recoveries ranged between 65 and 105%, and no matrix effects were observed. The proposed method has wide linear ranges, good inter- and intraday variability values (below 2.6 and 5.6%, respectively) and limits of detection between 0.49 μM (0.29 μg/g) and 4.31 μM (3.8 μg/g). The applicability of this analytical method was successfully tested in faecal samples from rats and humans.

Melamine (MAM) was employed as a pseudo template to prepare a molecularly imprinted polymer monolithic column which presents the ability of selective recognition to Triamterene (TAT), whose structure was similar to that of MAM. Methacrylic acid and ethylene glycol dimethacrylate were applied as functional monomer and cross-linker, respectively, during the in situ polymerization process. Chromatographic behaviors were evaluated, the results indicated that the molecularly imprinted polymer monolithic column possessed excellent affinity and selectivity for TAT, and the imprinting factor was high up to 3.99 when 7:3 of ACN/water v/v was used as mobile phase. In addition, the dissociation constant and the binding sites were also determined by frontal chromatography as 134.31 μmol/L and 132.28 μmol/g, respectively, which demonstrated that the obtained molecularly imprinted polymer monolith had a high binding capacity and strong affinity ability to TAT. Furthermore, biological samples could be directly injected into the column and TAT was enriched with the optimized mobile phase. These assays gave recovery values higher than 91.60% with RSD values that were always less than 3.5%. The molecularly imprinted monolithic column greatly simplified experiment procedure and can be applied to preconcentration, purification, and analysis of TAT in biological samples.

The molecularly imprinted SPE directly coupled to RP LC-MS/MS method has been developed and successfully validated for the determination of six hormones in water and sediment samples. The method is based on the use the home-made column filled with a molecularly imprinted sorbent (imprinted against estrogens) that was used under nonaqueous conditions. Thus, its high selectivity could be utilized resulting in low matrix components’ coextraction. The method showed excellent recovery (92–105%) and satisfactory sensitivity (LOQs water: 1.9–4.0 ng/L; LOQs sediment: 0.2–0.5 ng/g). The intra- and interprecision for water and sediment was in the range of 4.0–6.0% and 4.4–7.6%, respectively. Finally, 20 water and sediment samples collected from the Svratka river were analyzed. Only estrone was quantified in eight water samples (4.4–7.1 ng/L); no analytes were found in sediment samples.

Dopamine is easy to self-polymerize under alkaline conditions and the resultant polydopamine is easy to adhere to the surface of many organic and inorganic materials. Based on the characteristics of dopamine, in this paper, a new polydopamine functionalized monolithic silica column was successfully prepared for performing mixed-mode chromatography. The performance of the column was evaluated by the separation of different types of samples including alkylbenzenes, polycyclic aromatic hydrocarbons, aromatic acids, phenols, and bases. The mechanism for the separation of these compounds was studied and appeared to involve the mixed interactions containing π‒π, hydrophobic, electrostatic, and hydrophilic interactions.

The pressure drop and the plate height of chromatography columns packed with particles in the face-centered cubic, the body-centered cubic and the simple cubic configurations are calculated by a volume averaging method model. It is found that the Kozeny-Carman equation provides a reasonable prediction of the pressure drop when particles are in the face-centered cubic configuration, but overestimates the pressure drop when particles are in the body-centered cubic and the simple cubic configurations. The face-centered cubic configuration has the advantage to provide a smaller longitudinal dispersion coefficient than the body-centered cubic, the simple cubic, and the random configurations. The pressure drop and the plate height for slip flow through particles in the face-centered cubic configuration are lower than that for no-slip flow. The values of the smallest reduced plate height of columns packed with particles in the face-centered cubic configuration for no-slip flow and slip flow are about 0.084 and 0.059, respectively. The plate height of the ordered particle packing structures is smaller and the effect of slip flow on the plate height is less remarkable than results reported in literature.

This paper is devoted to application of ionic liquids as surfactants in LC of organic compounds, derivatives of 1,4-thiosemicarbazides. According to HPLC requirements the most advantageous conditions such as transparency for ultraviolet light, low CMC, additional inorganic salt additives, and appropriate organic solvent were established. The CMC was determined using conductivity measurements. Suitability of two different stationary phases: RP-C18 and cyanopropyl bonded phase was examined under micellar conditions. Chosen ionic liquid surfactant was compared to common traditional amphiphilic reagent – SDS. Elaborated on chromatographic micellar conditions were tested as a pilot technique for prediction of distribution coefficients of organic analytes in ionic liquid-based aqueous two-phase system.

It is meaningful to explore the possibility of improving the micro-GC column performance by adjusting the column cross-sectional shape. The objective of this study was to seek the column cross-sectional shape that results in larger plate number per meter than other shapes with the same cross-sectional area and the same flow resistance coefficient. We applied a model based on the volume averaging method to derive the expression of plate height for columns with arbitrary cross-sectional shapes, and conducted the shape optimization by combining the model and an optimization tool. By varying flow resistance coefficient, we obtained a series of optimal shapes. It is found that, the optimal shape with larger flow resistance coefficient is shallower and the related plate number per meter is larger. We predicted and optimized the performance of a micro-GC column reported in literature. The prediction agrees reasonably with experimental data. More than twice the plate number per meter of the original column was predicted by using a hypothetical column with one optimal cross-sectional shape.

A “ppseudo” targeted method using GC-MS-selected ions monitoring was applied to investigate the chemical characteristics of commercial cigarettes made in China and foreign countries. To identify the components and define the quantative ions for SIM acquisition, a quality control sample was analyzed using GC-MS full scan. Acquired data were treated with a homemade software. A peak table with 312 components and their related quantitation ions was achieved for SIM acquisition. Structure elucidation was performed using library searching, retention index, standard compounds, and fitted retention time. The fitted retention time was calculated by a linear correction curve obtained using measured and library retention time to verify compounds. A total of 90 compounds were elucidated. Chemical characteristics of different cigarette brands were investigated. The data acquisition was carried out in SIM mode. The principal component and the hierarchical clustering analyses showed that the Chinese domestic flue-cured cigarettes were significantly different from the domestic blended, the foreign flue-cured, and blended cigarettes. Sixty-seven differential compounds were defined using the nonparametric Mann–Whitney test and the group blending samples comparison. Chinese domestic flue-cured cigarettes have higher concentration of saccharides and lower concentration of organic acids and amino acids.

Quantitative structure–retention relationship (QSRR) models were developed for the retention indices of 505 frequently reported components of plant essential oils. Multiple linear regression was used to build QSRR models for the dimethyl silicone, dimethyl silicone with 5% phenyl groups, and polyethylene glycol stationary phases. We tried to improve the variable selection and modeling method based on prediction method for selecting the optimum descriptors from the molecular weight, 75 topological indices, and 170 atom-type E-state indices. The three-variable QSRR models perform high correlation coefficients of 0.937 for dimethyl silicone and 0.933 for dimethyl silicone with 5% phenyl groups stationary phase. Four variables were selected to developed QSRR model for the polyethylene glycol stationary phase. The leave-one-out and leave-many-out cross-validations, bootstrapping, and y-randomization test showed the three models are robust and have no chance correlation. The external validation with the test set showed the three models present high externally predictive power. The three models presented high-quality fit, internally, and externally predictive power. It is expected that the models can effectively predict retention indices of essential oils components without experimental value.

The methods for separation of R,S-tolterodine and R,S-methoxytolterodine enantiomers using sulfated α-, β-CD and phosphated-γ-CD by CE in acidic BGE based on Tris/phosphate pH 2.5 buffer were developed. Sulfated α- and β-CD allow anodic detection while phosphated-γ-CD allows only cathodic detection of the separated enantiomers. The influence of chiral selector (CS)'s concentration as well as the influence of composition and concentration of BGE on resolutions were studied. Reversal migration order of tolterodine and methoxytolterodine enantiomers was observed, when sulfated-α- and sulfated-β-CD were used. The developed methods with all three studied CSs, were validated and compared. All proposed methods enable determination of 0.2% of S-tolterodine as an optical impurity in pills, however the method with phosphated-γ-CD provided lower detection limit, better repeatability of peak areas and migration times, and also lower consumption of CS. Developed method employing phosphated-γ-CD that was applied for the determination of optical purity of R-tolterodine in commercial pills.

In this study, the partial filling technique on both polycationic polymer hexadimethrine bromide (HDB) modified capillary and eCAP neutral capillary were systematically compared in order to enhance the enantioseparation ability of bromobalhimycin as CE additive. The separation conditions, such as pH, the plug length, and the concentration of bromobalhimycin, etc., were optimized in order to obtain satisfactory separations. As expected, for all tested 28 N-benzoylated amino acids, up to five times higher enantioresolutions were obtained on the eCAP neutral capillary compared to that on the polycationic polymer hexadimethrine bromide modified capillary. Moreover, 26 of 28 tested racemic compounds were almost baseline- resolved without observing any interference from the front of the plug of bromobalhimycin. Although the limitation of longer running time on the neutral capillary, it allows the use of higher content of bromobalhimycin in the running buffer without any interference on the detection of analytes when enantioseparations are more difficult to obtain.

Polyamidoamine-grafted silica nanoparticles were synthesized, characterized and investigated for the feasibility as pseudostationary phases in alkaline buffer for separation of cationic and anionic proteins, viz., lysozyme, cytochrome C, gamma globulin, and myoglobin. Neither bare silica nanoparticles nor polyamidoamines nor their mixtures as pseudostationary phases could lead to simultaneous separation of the four proteins. However, polyamidoamine-grafted silica nanoparticles not only suppressed the irreversible wall adsorption of the cationic lysozyme and cytochrome C, but also provided selectivity toward all the proteins. We found that polyamidoamine generation two-modified silica nanoparticles were the optimum pseudostationary phases with respect to detection sensitivity and separation efficiency; presence of the nanoparticles at 0.01% in the running buffer of 12.5 mM tetraborate/phosphate at pH 9.1 resulted in baseline resolution of the four proteins.

This study reported a pH-mediated stacking CE coupled with ESI MS/MS method to determine the phosphorylation sites of three synthetic phosphopeptides containing structural isomers. These phosphopeptides mimic the phosphopeptides (amino acid residues 12–25) derived from the trypsin-digested products of human lamin A/C protein. The LODs were determined to be 118, 132 and 1240 fmol for SGAQASS¹⁹TpPL²²SPTR, SGAQASS¹⁹TPL²²SpPTR, and SGAQASS¹⁹TpPL²²SpPTR, respectively. The established method was employed to analyze the phosphorylation sites of the trypsin-digested products of glutathione S-transferase-lamin A/C (1–57) fusion protein that had been phosphorylated in vitro by cyclin-dependent kinase 1. The results indicated that this method is feasible to specifically determine the phosphorylation site from phosphopeptide isomers in the trypsin-digested products of a kinase-catalyzed phosphoprotein, which should benefit the investigation of protein kinase-mediated cellular signal transduction.

L-3,4-dihydroxyphenylalanine (L-DOPA) is a well-recognized therapeutic compound to Parkinson's disease. Tyrosine is a precursor for the biosynthesis of L-DOPA, both of which are widely found in traditional medicinal material, Mucuna pruriens. In this paper, we described a validated novel analytical method based on microchip capillary electrophoresis with pulsed electrochemical detection for the simultaneous measurement of L-DOPA and tyrosine in M. pruriens. This protocol adopted end-channel amperometric detection using platinum disk electrode on a homemade glass/polydimethylsiloxane electrophoresis microchip. The background buffer consisted of 10 mM borate (pH 9.5) and 0.02 mM cetyltrimethylammonium bromide, which can produce an effective resolution for the two analytes. In the optimal condition, sufficient electrophoretic separation and sensitive detection for the target analytes can be realized within 60 s. Both tyrosine and L-DOPA yielded linear response in the concentration range of 5.0–400 μM (R² > 0.99), and the LOD were 0.79 and 1.1 μM, respectively. The accuracy and precision of the established method were favorable. The present method shows several merits such as facile apparatus, high speed, low cost and minimal pollution, and provides a means for the pharmacologically active ingredients assay in M. pruriens.

A rapid and simple quantitative method for preconcentration and determination of haloperidol in biological samples was developed using ultrasound-assisted emulsification microextraction, based on the solidification of floating organic droplet combined with HPLC-DAD. The effects of several factors were investigated. A total of 30 μL of 1-undecanol as an extraction solvent was injected slowly into a glass-centrifuge tube containing 4 mL alkaline sample solution that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and the fine droplets of solvent were floated at the top of the test tube, then it was cooled in an ice bath and the solidified solvent was transferred into a conical vial, after melt, the analysis of the extract was carried out by HPLC. Under the optimal conditions, the extraction efficiencies were more than 90% and the preconcentration factors were obtained between 119–122. The LOQs were obtained between 4–8 μg/L and the calibration curves were linear within the range of 4–1000 μg/L. Finally this method was applied to the determination of haloperidol in plasma and urine samples in the range of μg/L and satisfactory results were achieved (RSDs <7%).

The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO₂/Al₂O₃ ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.

Pheromones guide adult sea lamprey (Petromyzon marinus) to suitable spawning streams and mates, and therefore, when quantified, can be used to assess population size and guide management. Here, we present an efficient sample preparation method where 100 mL of river water was spiked with deuterated pheromone as an internal standard and underwent rapid field-based SPE and elution in the field. The combination of field extraction with laboratory UPLC-MS/MS reduced the sample consumption from 1 to 0.1 L, decreased the sample process time from more than 1 h to 10 min, and increased the precision and accuracy. The sensitivity was improved more than one order of magnitude compared with the previous method. The influences of experimental conditions were assessed to optimize the separation and peak shapes. The analytical method has been validated by studies of stability, selectivity, precision, and linearity and by the determination of the limits of detection and quantification. The method was used to quantify pheromone concentration from five streams tributary to Lake Ontario and to estimate that the environmental half-life of 3kPZS is about 26 h.

This study describes the development of an analytical method based on active collection in a multisorbent Tenax TA/Carbograph 1TD tube, followed by thermal desorption and GC-MS for the determination of 16 volatile organic compounds in air samples. The analyzed compounds include ozone precursors and odor-causing compounds belonging to different chemical families (sulfur- and nitrogen-containing compounds, aldehydes, and terpenes). Two types of sorbents were tested and desorption conditions (temperature, time, and sampling, and desorption flow) were evaluated. External calibration was carried out using the multisorbent bed. Method detection limits in the range 0.2–2.0 μg m⁻³ for 1 L samples were obtained. The method was applied for determining the target compounds in air samples from two different wastewater treatment plants. Most compounds were detected and toluene, limonene, and nonanal were found in particularly high concentrations with maximum values of 438, 233, and 382 μg m⁻³, respectively.

In this research, the headspace solid-phase microextraction (SPME) coupled with GC flame ionization detector was applied for the determination of some monocyclic aromatic amines in real water and urine samples. A sol–gel technique was applied for the preparation of the SPME fibers. Two different sol–gel coatings, (PEG and poly(ethylene glycol) modified with multi-walled carbon nanotubes [PEG/CNTs]), were prepared and compared. Extraction efficiency of PEG/CNTs was better than PEG fiber in the same conditions. To obtain maximum extraction efficiency, some parameters such as desorption temperature and time, temperature and time of extraction, salt effect, pH, and stirring speed were investigated and optimized for PEG/CNTs fiber. Under optimized conditions, the LODs (S/N = 3) were in the range of 0.5–50 ng/L and limits of quantification (S/N = 10) were between 1 and 500 ng/L. Repeatability (n = 5) was in the range of 3.2–9.1% and reproducibility (n = 3) was obtained from 5.5 to 12.0%. The method was successfully applied to the analysis of real water and urine samples with recoveries from 63.7 to 97.0%.

Separation of polycyclic aromatic sulfur heterocycles among themselves and also from interferents in petrochemical matrices is a challenging task because of their low concentration, matrix complexity, and also due to the presence of polyaromatic hydrocarbons, as they present similar physico-chemical properties. Therefore, the objective of this work was preparation, characterization, and application of a stationary phase for separation of these compounds in a heavy gas oil sample and their identification by comprehensive two-dimensional gas chromatography. The stationary phase was prepared by grafting mercaptopropyltrimethoxisilane onto a silica surface, followed by palladium(II) chloride immobilization. Elemental analysis, thermogravimetry, nitrogen adsorption-desorption isotherms, infrared analysis, and scanning electron microscopy were performed to characterize this solid phase. Sulfur compounds were separated in an open column packed with the stationary phase and analyzed by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection. The number of compounds tentatively identified was 314 and their classes were thiophenes, benzotiophenes, dibenzothiophenes, naphthothiophenes, benzonaphthothiophenes, and dinaphthothiophenes. Separation among sulfur compounds and polyaromatic hydrocarbons was successful, which is a difficult goal to achieve with the traditionally employed solid phases. Some recalcitrant compounds (dibenzothiophenes with substituents of two and four carbons) were fully separated and tentatively identified.

A method based on dispersive liquid–liquid microextraction coupled with GC/MS was developed for quantitative analysis of the major organic pollutants listed in the United States Environmental Protection Agency method 8270 and the 15 European-priority polycyclic aromatic hydrocarbons in coking wastewater. The major parameters such as extraction solvent, dispersive solvent, solution pH, and extraction time were systematically optimized. The optimum extraction conditions were found to be: 15 μL mixture of 2:1 v/v carbon tetrachloride and chlorobenzene as the extraction solvent, 0.75 mL ACN as the dispersive solvent, solution pH of 8, and extraction time of 2 min. For the major pollutants listed in the United States Environmental Protection Agency 8270, the linear ranges were 0.1 to 100 mg/L, the enrichment factors ranged from 452 to 685, and the relative recoveries ranged from 67.5 to 103.5% with RSDs of 4.0–9.1% (n = 5) at the concentrations of 10 mg/L under the optimum extraction conditions. For the 15 polycyclic aromatic hydrocarbons, the linear ranges were 0.1 to 100 μg/L, the enrichment factors ranged from 645 to 723, and the relative recoveries ranged from 94.5 to 107.6% with RSDs of 4.6–9.0% (n = 5) at the concentrations of 10 μg/L. The usefulness of the developed method was demonstrated by applying it in the analysis of real-world coking wastewater samples.

In this study, the optimum extraction conditions for maximum recovery of the content of total phenolics (TPC) and total antioxidant abilities were analyzed for Malus baccata (Linn.) Borkh. using response surface methodology. The effects of ethanol percentage (X₁,%), ultrasonic power (X₂, W) and extraction temperature (X₃, °C) on the total phenolic content (Y₁) and antioxidant ability (Y₂) were evaluated. A second-order polynomial model produced a satisfactory fitting of the experimental data with regard to total phenolic content (R² = 0.9942, P < 0.0001) and antioxidant ability (R² = 0.9966, P < 0.0001). The optimized conditions were ethanol concentration of 61.0%, ultrasonic power of 308.6 W, extraction temperature of 51.1°C for TPC and 60.5%, 311.4 W, 51.6°C for antioxidant ability, the predicted values agreed well with the experimental values. Results implied that the major phenolic compounds in obtained extracts as chlorogenic acid, quercetin-3-gal/glu, quercetin-3-xyl/ara, phloretin-2-xyloside, quercetin-3- rhamnoside, and phloridzin.

Although various techniques have been employed to analyze drug metabolites, the metabolism of multicomponent herbal medicine has seldom been fully addressed. In contrast to chemical drugs, a number of compounds in herbal medicine could get into circulation and then be metabolized. Metabolism study on active constituents in herbal medicine is a good way for us to explain and predict a variety of events related to the efficacy and toxicity of herbal medicine. The present work aims to elucidate the multicomponent metabolic characteristics of a herbal medicine by the combination of plasma pharmacochemistry and microdialysis sampling. Anemarrhena asphodeloides, a well-known traditional Chinese medicine, was chosen as a model. After oral administration of A. asphodeloides saponin extract to rats, microdialysis samples were collected continuously in the jugular vein and analyzed by ultrahigh-performance LC/quadrupole-TOF MS. The identification of compounds in biosamples was achieved by accurate mass measurement and detailed fragmentation pathway analysis. The results showed that unbound constituents in blood circulation of the rat included seven parent saponins and six metabolites, which might be the potential active components in vivo. Among which, three metabolites have not been previously reported and were identified in this study. It is the first report on systemic metabolism of total saponins of A. asphodeloides in mammalian plasma.

Several Acalypha australis Linn. species are used in traditional medicine in Southeast Asia. In this work, the ultra-performance liquid chromatography/mass spectrometry fingerprints and the antibacterial activities of A. australis Linn. were investigated. An in-depth discussion on the reliability of identifying and obtaining potentially active compounds by spectrum-effect relationship and semi-preparative high performance liquid chromatography was conducted. The result shows that gallic acid and a compound with molecular weight of 634.1 in the fingerprints were the main antibacterial compounds. Compared to the crude extract of A. australis Linn., both compounds increase the antibacterial efficacy 10 to 20 times. Compounds with molecular weights of 154.0, 292.0, and 485.1 in the fingerprints were the auxiliary antibacterial compounds. Through the entire isolation procedure, we obtained these antibacterial compounds with purities of 92.53, 87.98, 90.73, 89.36, and 88.14%, respectively. This work provides a general model of the combination of ultra-performance liquid chromatography/mass spectrometry fingerprinting and antibacterial test to study the spectrum-effect relationships of A. australis Linn. This model can be used to discover further the active compounds of this herb.

The preprocessing of chromatograms is essential to modern chromatography for further qualitative and quantitative analysis, especially when chromatographic instruments are used for herb products analysis involving large number of samples. To accurately compare and analyze the obtained chromatograms, it is necessary to preprocess, especially align retention time shifts. Here moving window fast Fourier transform (FFT) cross-correlation is introduced to perform nonlinear alignment of high-throughput chromatograms. Since elution characteristics of chromatograms will produce local similarity in retention time shifts, moving window procedure seems to be a better substitute of segmentation steps. The retention time shifts can be calculated and accelerated by FFT cross-correlation. The artifacts can be detected and eliminated from the retention time shifts profile since the continuity of moving window procedure. The proposed method is demonstrated in comparison with recursive alignment by FFT on chromatographic datasets from herb products analysis. It is shown that the proposed method can address nonlinear retention time shift problem in chromatograms with the simple moving window procedure, which will not introduce segments size optimization problem. In additional, the parameters are intuitive and easy to adjust, which makes it off-the-shelf toolbox for alignment of chromatograms.