| New form of appearance for special issues. As we are living in the electronic era, all manuscripts submitted for publication in a special issue will be published individually in regular issues as soon as they are accepted. The first page includes a footnote showing that that paper is included in the virtual special issue accessible through the internet. |
The virtual special issues on Monoliths covers a variety of topics that span from the modeling, preparation and application of home-made monoliths, to applications of commercially available monolithic columns. Separation Science in modern times means to deal with several challenges: Sample complexity, speediness, demand of new column formats, polar compounds, etc. In the meantime, scientists know a lot of monolithic material. However, the more you know the more you would like to understand structures and processes which often leads to new material.
Enjoy the reading.
Flow-through immobilized enzyme reactors based on monoliths: I. Preparation of heterogeneous biocatalysts
Evgenia G. Vlakh and Tatiana B. Tennikova
This paper represents the first part of an extensive review devoted to flow-through immobilized enzyme reactors (IMERs) based on monoliths and describes the most of approaches found for enzyme immobilization on monolithic supports. The use of modern monolithic stationary phases characterized by low operative backpressure and fast mass transfer, high enzyme loading, and biocatalytic activity has great adventures and obvious perspectives to be applied for modern IMERs construction. The simplicity of monolithic columns preparation and their modifications in combination with high stability of discussed IMERs, and, consequently, long lifetime, as well as the possibility of their incorporation into automated systems make these functional monolithic devices quite useful in proteomics, pharmaceutics, biotechnology, organic synthesis, and others.
Keywords: Enzymes, Flow-through system, Monoliths, Stationary phases
Flow-through immobilized enzyme reactors based on monoliths: II. Kinetics study and application
Evgenia G. Vlakh and Tatiana B. Tennikova
This the second part dealing with flow-through immobilized enzyme reactors based on monoliths. Here, analysis of kinetic data and discussion of the results on the application of such reactors in biotechnology, pharmaceutics, organic synthesis, etc., are presented. In the last decade, the application of monolithic materials has rapidly expanded to the realization of flow-through bioconversion processes. Up to these days, different classes of enzymes such as hydrolases, lyases, and oxidoreductases have been immobilized on organic, inorganic, or hybrid monolithic materials to prepare the effective flow-through enzymes reactors for application in proteomics, biotechnology, pharmaceutics, organic synthesis, and biosensoring.
Keywords: Biocatalyst, Enzyme application, Enzyme kinetics, Monoliths
Column technology – organic polymers
Ring-opening metathesis polymerization-derived, lectin-functionalized monolithic supports for affinity separation of glycoproteins
Rajendar Bandari, Jürgen Kuballa and Michael R. Buchmeiser
A versatile method for the preparation and functionalization of hydrophilic polymeric monoliths by ring-opening metathesis polymerization has been developed. The prepared PEG-amine-monoliths were successfully used for the immobilization of lectin i.e. LCH and successfully tested for their performance in the separation of glucose oxidase using affinity chromatography.
Keywords: Bioseparation, Lectin affinity chromatography, Monoliths, ROMP
Preparation and application of a novel zwitterionic monolithic column for hydrophilic interaction chromatography
Zhenghua Liu, Yongbo Peng, Tingting Wang, Guangxin Yuan, Qiaoxuan Zhang, Jialiang Guo and Zhengjin Jiang
A porous poly(SPP-co-EDMA) monolithic column has been successfully prepared based on the copolymerization of SPP and EDMA in the presence of methanol as the porogen. The optimized poly(SPP-co-EDMA) monolithic column exhibited satisfactory selectivity for a range of neutral, acidic and basic test compounds. It could be demonstrated that this monolithic column is an alternative for separating complex samples.
Keywords: EDMA, Methanol, Monoliths, One-step in situ copolymerization, Reproducibility
Cation exchange/hydrophobic interaction monolithic chromatography of small molecules and proteins by nano liquid chromatography
Cemil Aydoğan, Fatma Yılmaz and Adil Denizli
A novel LMA-based boronate functionalized monolithic column was prepared and characterized. To evaluate the monolithic structure, different binary porogenic solvents were used and optimized while the ratio of functional monomer to cross-linker was kept constant. The monolithic column indicated mixed mode properties. Cation exchange/hydrophobic interactions of small molecules and proteins were successfully demonstrated using the prepared column. The protein interactions of the prepared column showed good specificity toward glycoprotein. Boronate functionalized monolithic columns could be a promising tool for cis-diol biomolecules analysis and identification.
Keywords: Biomolecules analysis, Capillary column, Hydrophilic monoliths, Nano LC, Vinyl phenyl boronic acid
A novel method to prepare monolithic molecular imprinted polymer fiber for solid-phase microextraction by microwave irradiation
Ya-Feng Jin, Yu-Ping Zhang, Ming-Xian Huang, Lian-Yang Bai and Milton L. Lee
A novel procedure for a rapid, reproducible, and fast preparation of MIP fibers for SPME in a batch mode within 4.5 min is described. The fiber characteristics, extraction efficiency, and selectivity were directly compared to the performance of an analogous non-imprinted SPME fiber. Applications of MIP-SPME for concentrating and clean-up of DMP and other structurally related compounds including dibutyl phthalate and di-n-octylo-phthalate in bottled beverages were investigated.
Keywords: Batch mode SPME, Dimethylphthalate, Imprinting polymerization, Monoliths
New zwitterionic polymethacrylate monolithic columns for one- and two-dimensional microliquid chromatography
Pavel Jandera, Magda Staňková and Tomáš Hájek
0.53 and 0.32 mm id monolithic microcolumns were prepared by in situ copolymerization of a zwitterionic sulfobetaine functional monomer with bisphenol A glycerolate dimethacrylate (BIGDMA) and dioxyethylene dimetacrylate crosslinkers. The new zwitterionic monolithic columns are highly orthogonal, with respect to alkyl silica stationary phases, not only in the hydrophilic-interaction mode but also in the RP mode. When the 2D setup with the sulfobetaine–BIGDMA column was used for repeated sample analysis, with alternating gradients of decreasing (hydrophilic-interaction mode), and increasing (RP mode) concentration of acetonitrile on the sulfobetaine–BIGDMA column in the first dimension, useful complementary information on the sample could be obtained.
Keywords: Flavonoids, HILIC, Monoliths, Phenolic compounds,
Column technologies – silica and hybrids
Fabrication of large-sized silica monolith exceeding 1000 mL with high structural homogeneity
Riichi Miyamoto, Yukiko Ando, Chie Kurusu, Hong-zhi Bai, Kazuki Nakanishi and Masamichi Ippommatsu
The fabrication of large monolithic silica applicable to a high-performance chromatographic medium was successfully fabricated in a scale up to 1000 mL by the enlargement of a small pore size. The newly developed method of internal cooling with ice cubes stabilized and homogenized the temperature distribution within the whole mass of reaction solution, resulting in the sharp pore size distributions with the homogeneous skeleton structures of monolithic silica. Preliminary results on high-speed separation of peptides and proteins, within 5 min, by the octadecylsilylated silica monolith of the above production have also been demonstrated.
Keywords: LC, Monoliths, Preperative scale, Protein purification, Silica
Polydopamine-functionalized monolithic silica column for mixed-mode chromatography
Qiaoli Zhou, Peiling Yang, Xing Xiao and Li Jia
A new PDA monolithic silica column was prepared. The modification procedure is based on the self-polymerization of dopamine. PDA adhering to the surface of monolithic silica skeleton is very simple. Nonpolar and polar, acidic and basic compounds including PAHs, alkylbenzenes, aromatic acids, phenols, nucleoside, and bases obtained good and fast separation on the new PDA column. The separation capability of the column for these compounds demonstrated that the column could provide different retention mechanisms involving π–π, hydrophobic, electrostatic, and hydrophilic interactions between the analytes and the stationary phases.
Keywords: Hydrophilic interactions, π–π Interactions, Silica-based monoliths
Photografting as a versatile, localizable, and single-step surface functionalization of silica-based monoliths dedicated to microscale separation techniques
Racha El-Debs, Vincent Dugas and Claire Demesmay
A surface functionalization way of silica monoliths with a rapid, simple, versatile, and localizable photografting step was developed. First, the elaboration of a photoreactive layer at the surface of monoliths was optimized. Functionalization with [γ-(methacryloyloxy)propyl]trimethoxysilane at 80°C in a hydro-organic solution with triethylamine as a catalyst reached the highest density of methacrylate photoactive moieties on silica surfaces. These methacrylate reactive surfaces were subsequently photografted within few minutes with acrylate monomers bearing alkyl chains (C12 and C18). The photografting efficiency was determined by monitoring the retentive properties of monoliths in the RP mode.
Keywords: γ-MAPS, Monoliths, Nano-LC, Surface functionalization
Photopolymerized organo-silica hybrid monolithic columns: Characterization of their performance in capillary liquid chromatography
Anna-Marie Karen Weed, Jill Dvornik, John Jacob Stefancin, Afua Asantewaa Gyapong, Frantisek Svec and Zuzana Zajickova
Efficient porous organo-silica hybrid monolithic columns for HPLC can be prepared by using the sol–gel technique combined with UV light or thermally initiated polymerization utilizing a common initiator AIBN. The ability to separate both nonpolar and polar compounds as well as analytes varying in planarity in RP mode represents positive feature of these monolithic columns. Both silanols and polymerized methacrylate functionalities are present at the pore surface. In addition, the pore size distribution indicates that these monoliths can be useful in rapid separations of proteins and other large molecules.
Keywords: Hybrid, Monoliths, Organo-silica, Photopolymerization, Sol–gel technique
Photopolymerized sol–gel monoliths for separations of glycosylated proteins and peptides in microfluidic chips
Miriam H. Levy, Joel Plawsky and Steven M. Cramer
Photopolymerized silica sol–gel monoliths functionalized with boronic acid ligands have been developed for protein and peptide separations in PDMS microfluidic devices. Batch experiments showed that boronic acid modified monoliths were selective toward cis-diol-containing compounds. This work might help to set the stage for a variety of more complex lab-on-a-chip proteomic applications whereby a boronic acid functionalized monolith can be used to extract glycopeptides from a complex mixture prior to further analysis.
Keywords: Boronic acid, Glycoproteins, Monoliths, Polydimethylsiloxane, Sol–gel technique
Organic–inorganic hybrid fluorous monolithic capillary column for selective solid-phase microextraction of perfluorinated persistent organic pollutants
Xiyue Xiong, Zihui Yang, Yongbin Huang, Linbo Jiang, Yingzhuang Chen, Yao Shen and Bo Chen
A novel construction strategy of monolithic capillary column for selectively enriching perfluorinated persistent organic pollutants was proposed. The organic–inorganic hybrid fluorous monolithic capillary column was synthesized by a "one-pot" approach via the polycondensation of γ-methacryloxypropyltrimethoxy-silane, then in situ copolymerization of 1H,1H,7H-dodecafluoroheptyl methacrylate and vinyl group on the precondensed siloxanes. The results demonstrated that the optimal column possessed good mechanical stability and high permeability. It is possible to concentrate trace amounts of perfluorooctanoic acid and perfluorooctane sulfonate in water about 160 times to their original concentrations by this monolithic column.
Keywords: Enrichment, Monoliths, One-step in situ copolymerization, Selectivity
Preparation and characterization of octadecyl acryl monoliths for capillary electrochromatography by photochemical, thermal, and chemical initiation
Aarón Escrig-Doménech, Isabel Ten-Doménech, Ernesto F. Simó-Alfonso and José M. Herrero-Martínez
ODA-based monolithic columns for CEC have been prepared using either UV irradiation, thermal, or chemical initiation. Columns synthesized by UV and chemical initiation showed higher permeabilities and better efficiencies than those prepared by thermal treatment. These good features make both initiation modes excellent candidates to be used in the preparation of long monolithic columns and miniaturized devices. All three initiating systems provided satisfactory column-to-column and batch-to-batch reproducibilities in their electrochromatographic behavior.
Keywords: Acrylate ester-based monolithic columns, Hybrid technique, Initiating systems, Lauroyl peroxide
Open tubular columns with mixed-mode reversed-phase and weak anion-exchange stationary phase for capillary electrochromatography
Jie Lei and Xiangmin Zhang
Silica-based, open-tubular capillary columns bearing C8, amine, and silanol moieties in the inner surface were produced by sol–gel approach. The feature, to easily control both the direction and magnitude of EOF by changing the pH values of the mobile phas makes it possible to separate a wide range of species in a single capillary. An initial study demonstrated that the mixed-mode capillaries are powerful in the separation of simple aromatic compounds
Keywords: Capillary electrochromatography, Mixed-mode retention, Monoliths, Open tubular columns, Sol–gel method, Switchable electroosmotic flow
Simultaneous separation of water- and fat-soluble vitamins in isocratic pressure-assisted capillary electrochromatography using a methacrylate-based monolithic column
Hiroki Yamada, Shinya Kitagawa and Hajime Ohtani
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. The use of a highly sensitive detection method such as MS/MS will be effective to detect small amount of vitamins in pharmaceutical preparations.
Keywords: Electrochromatography, Fat-soluble vitamins, Isocratic elution, Methacrylate-based monolithic column, Volatile mobile phase, Water-soluble vitamins
Comparison of various silica-based monoliths for the analysis of large biomolecules
Karine Vuignier, Szabolcs Fekete, Pierre-Alain Carrupt, Jean-Luc Veuthey and Davy Guillarme
Three types of silica-based monoliths, the first and second generations of commercial silica monolithic columns and a wide-pore prototype monolith were compared for the analysis of large biomolecules. The retention and selectivity remained quite close between the three columns, except a few changes in selectivity with the wide-pore phase, attributed probably to a larger amount of accessible residual silanols. On the other hand, the band broadening and peak tailing were always less pronounced with the wide-pore silica-based monolith, proving that this column could be of interest for biomolecules. One of the major issues with any of these silica-based monoliths is the strong adsorption of large biomolecules (principally with mAbs fragments of more than 25 kDa).
Keywords: Monoclonal antibodies, Peptides, Proteins, Protein adsorption, Silica-based monoliths, Wide pores
Selectivity tuning via temperature pulsing using low thermal mass liquid chromatography and monolithic columns
Matthias Pursch, Patric Eckerle, Binghe Gu, Jim Luong, Hernan J. Cortes
The Chromolith CapRod RP-18e capillary with an efficiency of up to 160 000 plates/m was used for the separation of an insecticide mixture using both mobile phase and various temperature gradients. Temperature increasing and decreasing gradients as well as very fast temperature pulses were applied, and considerable peak shifts and selectivity increases were observed for given temperature conditions. The concept of applying short temperature pulses during a separation shows promise for increasing resolution for difficult separations and can provide a relatively simple means to solve coelution problems.
Keywords: Low-thermal mass LC, Monoliths, Temperature gradient
Sensitive monitoring of penicillin antibiotics in milk and honey treated by stir bar sorptive extraction based on monolith and LC-electrospray MS detection
Xiaojia Huang, Linli Chen, Meng Chen, Dongxing Yuan, Shuyu Nong
Stir bar sorptive extraction based (SBSE) on poly(vinylimidazole-divinylbenzene) (VIDB) monolithic coating material was successfully applied to simple extraction of polar penicillins in milk and honey. The proposed method is simple, because no additional step to eliminate fats, proteins in milk and sugar in honey is needed. At the same time, the combination of SBSE-VIDB with HPLC/ESI-MS/MS realized the highly sensitive determination of penicillin residues in milk and honey. Therefore, this method will be useful and practical in future residual monitoring of AMO, AMP, PEG, OXA, CLO, and DIC in food.
Keywords: Antibiotics, Honey, Milk, Monoliths, Penicillin, Poly(vinylimidazole-divinylbenzen), Stir bar sorptive extraction
Determination of rimantadine in human urine by HPLC using a monolithic stationary phase and on-line post-column derivatization
Constantinos K. Zacharis, Paraskevas D. Tzanavaras and Athanasios G. Vlessidis
The proposed HPLC-PCD method for the determination of rimantadine in human urine samples offers some interesting features: (i) this is the first report of an HPLC method coupled to on-line PCD for either rimantadine or its analogous compounds (e.g. amantadine or memantine); (ii) the use of OPA/NAC as derivatizing reagents and fluorimetric detection enables the sensitive determination of rimantadine at concentration levels that are in accordance with the pharmacokinetic characteristics of the analyte; (iii) employing a monolithic stationary phase for HPLC separation and the Oasis HLB SPE cartridges for sample preparation resulted in clear chromatograms, while no matrix effect was observed.
Keywords: Amantadine analogues, Analytical derivatization, Biological samples, LC, Monoliths
Selective recognition of Triamterene in biological samples by molecularly imprinted monolithic column with a pseudo template employed
Xiao-Yun Zhao, Hong-Wu Zhang, Zhen-Jie Liang, Ya-Ping Shu, Yong Liang
Novel imprinted monolithic columns were prepared by in situ thermal-initiated polymerization. Melamine, the analog of triamterene (TAT), was selected as the pseudo-template molecule, thereby avoiding leakage of the template and influence of the detection accuracy. Methacryclic acid was used as monomer, ethylene glycol dimethacrylate as cross-linker, methanol/water and dodecanol mixtures as the porogenic solvents. The obtained imprinted monoliths showed high affinity to TAT in aqueous environment and were successfully used for selective separation and determination of TAT from human urine and serum. The samples could be directly injected into the monolithic column and separation, enrichment, and detection were carried out in a single step. This method simplifies the pretreatment procedure, especially for complex biological samples, and shortens the analysis time.
Keywords: Biological samples, Molecular imprinted polymer, Monoliths, Pseudo template, Triamterene
Polymer monolithic capillary microextraction combined on-line with inductively coupled plasma MS for the determination of trace rare earth elements in biological samples
Lin Zhang, Beibei Chen, Man He and Bin Hu
A poly(IDA-GMA-TRIM) monolithic capillary was prepared and used for on-line CME-MCN-ICP-MS analysis of trace/ultratrace REEs in biological samples (urine and serum). The method features high sensitivity and sample throughput, low sample consumption and contamination risks, easy operation, wide pH application range, and good tolerance to the matrix interferences. Therefore, the developed approach provides an attractive alternative for the analysis of REEs in rare and complex samples at nanogram per liter levels.
Keywords: Complex samples, Limited sample volumes, Polymer monoliths, Sample pretreatment technique