| 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.
The virtual special issue on Monoliths only starts collecting papers. It will grow during the next weeks and months. As soon as new articles have been added to the virtual special issue you will be informed here. Please bookmark and enjoy the reading.
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
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
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
In this work, we developed a surface functionalization way of silica monoliths with a rapid, simple, versatile, and localizable photografting step. The elaboration of a photoreactive layer at the surface of monoliths was first optimized. The functionalization with [γ-(methacryloyloxy)propyl]trimethoxysilane at 80°C in a hydro-organic solution containing triethylamine as catalyst allows reachng 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. The retention factors are of the same order of magnitude as highly retentive columns obtained by modification of silica surface with long-alkyl chain silanes or by thermal polymerization of long-alkyl chain monomers. It was also verified that such grafting neither impaired the efficiency of the monolithic stationary phase (Hmin = 6–8 μm in nano-LC) nor its permeability (about 6 × 10−14 m2). Further, it was also demonstrated that photografting is localizable in nonmasked defined areas. Results obtained in anion-exchange chromatography after photopolymerization of [2-(methacryloyloxy)ethyl]trimethylammonium chloride are presented as well to demonstrate the versatility of the developed approach.
Keywords: Monoliths, Nano-LC, Photografting, Surface functionalization
Flow-through immobilized enzyme reactors based on monoliths: II. Kinetics study and application
Evgenia G. Vlakh and Tatiana B. Tennikova
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. Current review describes the results of kinetic study and specialties of flow-through immobilized enzyme reactors based on the existing monolithic materials.
Keywords: Biocatalyst, Enzyme application, Enzyme kinetics, Flow-through bioreactor, Immobilized emzyme, Monoliths
Ring-opening metathesis polymerization-derived, lectin-functionalized monolithic supports for affinity separation of glycoproteins
Rajendar Bandari, Jürgen Kuballa and Michael R. Buchmeiser
Lectin-functionalized monolithic columns were prepared within polyether ether ketone (PEEK) columns (150 × 4.6 mm id) via transition metal-catalyzed ring-opening metathesis polymerization of norborn-2-ene (NBE) and trimethylolpropane-tris(5-norbornene-2-carboxylate) (CL) using the first-generation Grubbs initiator RuCl2(PCy3)2(CHPh) (1, Cy = cyclohexyl) in the presence of a macro- and microporogen, i.e. of 2-propanol and toluene. Postsynthesis functionalization was accomplished via in situ grafting of 2,5-dioxopyrrolidin-1-yl-bicyclo[2.2.1]hept-5-ene-2-carboxylate to the surface of the monoliths followed by reaction with α,ω-diamino-poly(ethyleneglycol). The pore structure of the poly(ethyleneglycol)- derivatized monoliths was investigated by electron microscopy and inverse-size exclusion chromatography, respectively. The amino-poly(ethyleneglycol) functionalized monolithic columns were then successfully used for the immobilization of lectin from Lens culinaris hemagglutinin. The thus prepared lectin-functionalized monoliths were applied to the affinity chromatography-based purification of glucose oxidase. The binding capacity of Lens culinaris hemagglutinin-immobilized monolithic column for glucose oxidase was found to be 2.2 mg/column.
Keywords: Bioseparation, Glycoprotein, Lectin affinity chromatography, Monoliths, ROMP
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
In this paper, a new approach to prepare monolithic molecularly imprinted polymer (MIP) fibers for solid-phase microextraction is proposed with the help of microwave irradiation. Imprinting polymerization was carried out within silica capillaries in 4.5 min, using dimethyl phthalate (DMP) as a template molecular, α-methacrylic acid as a functional monomer and ethylene dimethacrylate as a crosslinker, acetonitrile as the porogenic solvent. The synthesis was optimized by varying the ratio of template/monomer and different volume of porogen. The resulted MIP fibers were obtained after silica being etched away with a controlled length of 1 cm, and subsequently characterized by SEM. In order to increase the selective extraction of DMP, factors affecting the extraction including extraction time, salt concentration, desorption time, and desorption solvents were investigated for solid-phase microextraction procedures in detail. The selectivity coefficients, defined as the extraction amount ratio of MIP to its nonimprinting fiber, were 5.6, 2.6, and 1.4 for DMP and its counterpart including dibutyl phthalate and di-n-octylo-phthalate, respectively. The resulted fibers were also applied to detect DMP, dibutyl phthalate, and di-n-octylo-phthalate in bottled beverage samples coupled to HPLC and resulted in relative recoveries of up to 73.8–98.5%, respectively.
Keywords: Dimethylphthalate, Microwave irradiation, Molecular imprinted polymer, Monoliths, Solid-phase microextraction