Preparation of poly(N-vinylpyrrolidone-co-pentaerythritol triacrylate) monolithic column for hydrophilic interaction chromatography

A method for the preparation of poly(N-vinylpyrrolidone-co-pentaerythritol triacrylate copolymerization)-based monolithic capillary column was reported for the separation of polar small molecular weight compounds with nano-liquid chromatography in hydrophilic interaction chromatography mode. The monolithic columns were prepared by in situ copolymerization of N-vinylpyrrolidone and a cross-linker pentaerythritol triacrylate in a binary porogenic agent consisting of methanol and water. The composition of the polymerization solution was systematically optimized in terms of column permeability, theoretical plate number, asymmetric factor, and retention factor. A typical hydrophilic chromatography retention mechanism was observed with a mobile phase composed of a high content of organic solvent. The preparation method is simple and robust, the precursor N-vinylpyrrolidone is chemically stable, cheap, and easily available. The N-vinylpyrrolidone-based hydrophilic interaction chromatography stationary phase displays satisfactory separation selectivity for a range of polar test analytes, including benzoic acid derivatives, nucleosides, and phenols.

Universal gold nanoparticle modified hybrid monolithic substrate developed for facile in-column post-functionalization

Organic-inorganic hybrid monolithic columns, due to the comprehensive advantages, have been applied as promising solid-phase separation matrices for pretreatment of complex samples in biomedical and environmental analyses, however, a tremendous time and efforts are cost to optimize the preparation methods of hybrid monolithic columns with different functional groups for various target analytes. Herein, we proposed a strategy to develop basic hybrid monolithic column materials for flexible and facile post-functionalization. Three kinds of single-functionalized (amine, thiol, and carboxyl) and two kinds of bi-functionalized (amine and thiol, and amine and carboxyl) hybrid monolithic columns were immobilized with gold nanoparticles (GNPs) as intermediary bridge to construct the universal substrates. The GNPs adsorption capacities of the five hybrid monoliths were compared through qualitative characterization and quantitative analysis. Thioglycolic acid (TGA) and an aptamer against human α-thrombin were respectively used for further functionalizing the substrates to select the most suitable hybrid monolith for optional post-functionalization. It was reported for the first time that the coverage density of TGA on functionalized monolithic column modified by GNPs was 168.41 nmol μL^-1. Notably, the coverage density (2205.8 pmol μL^-1) of the aptamer decorated on the hybrid monolithic column was significantly higher than most other similar materials in published works. After that, the aptamer functionalized hybrid monolithic column screened out was applied for the solid-phase microextraction of thrombin, which possessed excellent adsorption selectivity in interference experiment. Consequently, the developed GNPs modified amine- and thiol-bi-functionalized hybrid monolithic column is an attractive universal substrate to realize easy and efficient post-modification of separation materials for other target analytes in complex samples avoiding a lot of time and labor consumption in the optimization of process preparation.

A novel one-pot strategy of preparation of N-phenylacrylamide-styrene co-polymer open tubular capillary column for peptides separation

An open tubular capillary column (100 μm internal diameter and 120 cm length) was first fabricated with N-phenylacrylamide and styrene copolymer layer on the inner surface by in situ one-pot strategy, while ethylene dimethacrylate was used as the cross-linker. The pretreated silica-fused capillary was reacted with 3-trimethoxysilyl propyl methacrylate to attach a double-bond ligand onto the inner surface of the capillary. Further, a thick and stabile copolymer layer was generated on the inner surface of the capillary by the novel method in situ one-pot reaction of styrene-N-phenylacrylamide. The effects of reaction temperature and composition of the polymerization mixture on the morphology and permeability of the copolymer were investigated. The separation performance of the fabricated polymer columns were validated by separation of five synthetic peptides. The excellent efficiency (188 500 plates/m) of 100 μm internal diameter open tubular column with the separation media prepared by mixed one-pot copolymerization has not been achieved via the isocratic elution mode. The column to column, intraday, and interday repeatabilities evaluated from the relative standard deviation were found better than 4%, exhibiting considerable repeatability of the column.

Adjusting the chromatographic properties of poly(ionic liquid)-modified stationary phases by substitution on the imidazolium cation

Poly(ionic liquid)-modified stationary phases can have multiple interactions with solutes. However, in most stationary phases, separation selectivity is adjusted by changing the poly(ionic liquid) anions. In this work, two poly(ionic liquid)-modified silica stationary phases were prepared by introducing the cyano or tetrazolyl group on the pendant imidazolium cation on the polymer chains. Various analytes were selected to investigate their mechanism of retention in the stationary phases using different mobile phases. Two poly(ionic liquid)-modified stationary phases can provide various interactions toward solutes. Compared to the cyano-functionalized poly(ionic liquid) stationary phase, the tetrazolyl-functionalized poly(ionic liquid) stationary phase provides additional cation-exchange and π-π interactions, resulting in different separation selectivity toward analytes. Finally, applicability of the developed stationary phases was demonstrated by the efficient separation of nonsteroidal anti-inflammatory drugs.

Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC

In this study, poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) polymeric monoliths were in situ developed within 0.75 mm i.d. poly(ethylene-co-tetrafluoroethylene) (ETFE) tubing by UV polymerization via three different free-radical initiators (α,α'-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMPP). The influence of the nature of each photo-initiator and irradiation time on the morphological features of the polymer was investigated by scanning electron microscopy, and the chromatographic properties of the resulting microbore columns were evaluated using alkyl benzenes as test substances. The beds photo-initiated with MTMPP gave the best performance (minimum plate heights of 38 μm for alkyl benzenes) and exhibited a satisfactory reproducibility in the chromatographic parameters (RSD < 11%). These monolithic columns were also successfully applied to the separation of phenylurea herbicides, proteins and a tryptic digest of β-casein.

A reversed-phase/hydrophilic bifunctional interaction mixed-mode monolithic column with biphenyl and quaternary ammonium stationary phases for capillary electrochromatography

A novel RPLC/HILIC mixed-mode monolithic column with biphenyl and quaternary ammonium stationary phases is synthesized for capillary electrochromatography.