Poly(glyceryl monomethacrylate-co-ethylene glycol dimethacrylate) monolithic columns with incorporated bare and surface modified gluconamide fumed silica nanoparticles for hydrophilic interaction capillary electrochromatography.

This research article presents the preparation and characterization of monolithic capillary columns with incorporated bare fumed silica nanoparticles (FSNPs) and surface coated gluconamide FSNPs and their subsequent use in hydrophilic interaction capillary electrochromatography (HI-CEC) of small relatively polar solutes. The monolithic support was based on the in situ polymerization of glyceryl monomethacrylate (GMM) and ethylene glycol dimethacrylate (EDMA) yielding the poly(GMM-co-EDMA) monolith for the incorporation of bare and gluconamide-FNSPs. The poly(GMM-co-EDMA) monolith functioned as a true "support" for both types of polar FSNPs "stationary phases". In other words, monolithic capillary columns with "FSNPs stationary phases" were obtained in the sense that the contribution of the monolith proper to solute' retention was at its minimum. The gluconamide-FSNPs were obtained by reacting the FSNPs with the polar organosilane N-(3-triethoxysilylpropyl)gluconamide either by a pre- or on-column approach yielding p-gluconamide-FSNPs or o-gluconamide-FSNPs, respectively. While the p-gluconamide-FSNPs was coated by an oligosiloxane gluconamide layer as revealed by thermogravimetric analysis, the o-gluconamide-FSNPs are thought to be covered with a monomeric layer of gluconamide ligands as was manifested by the higher plate number obtained on the latter than on the former gluconamide-FSNPs incorporated monolithic columns. In the on-column modification process of FSNPs, the reaction was performed in a closed system whereby atmospheric water vapor are not available to cause the polymerization of the trifunctional organosilane N-(3-triethoxysilylpropyl)gluconamide. Also, the fact that the o-gluconamide-FSNPs incorporated monoliths were made from bare-FSNPs incorporated monoliths may indicate that the bare FSNPs were better dispersed into the monolithic matrix than the p-gluconamide-FSNPs, a condition that might have further contributed to the lower plate count obtained on p-gluconamide- than o-gluconamide-FSNPs incorporated monolithic columns. Overall, o-gluconamide-FSNPs stationary phases and to a lesser extent bare-FSNPs stationary phases proved useful in HI-CEC of small polar solutes, including DMF, formamide, thiourea, some phenols and nucleobases.

Organic polymer-based monolithic stationary phases with incorporated nanostructured materials for HPLC and CEC.

This review article is concerned with the recent advances made in the field of organic polymer-based monoliths with incorporated nanostructured materials (NSMs) for use in liquid chromatography and capillary electrochromatography. It covers the pertinent literature published over the last 7-8 years with a total of 56 references. The present article has two distinct parts: one major part encompassing "traditional" organic polymer-based monoliths modified with NSMs and a minor part on cryogels modified with NSMs.

Monolithic capillary columns consisting of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) and their diol derivatives with incorporated hydroxyl functionalized multiwalled carbon nanotubes for reversed-phase capillary electrochromatography.

Two types of monolithic stationary phases with incorporated hydroxyl functionalized multiwalled carbon nanotubes (OH-MWCNTs) were introduced and evaluated, namely, the poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) monolith, denoted as poly(GMA-co-EDMA), and a diol derivative of the poly(GMA-co-EDMA) monolith. The diol derivative monolith was obtained by subjecting the poly(GMA-co-EDMA) monolith with physically incorporated OH-MWCNTs to an acid treatment with 0.1 M sulfuric acid at a moderate temperature of 50 °C for a total of 7.5 h. Also, the poly(GMA-co-EDMA) monolith with both physically and covalently incorporated OH-MWCNTs was prepared by subjecting the physically incorporated monolithic column to a Lewis acid catalyzed reaction in the presence of BF3 in order to react some of the OH-MWCNTs with the epoxy rings of the poly(GMA-co-EDMA) monolith. In all cases, the OH-MWCNTs were subjected to high power sonication at an output power of 10 W for 15 min with the aim of better dispersing the incorporated nanotubes into the monoliths under investigation. In fact, high power sonication yielded columns with a relatively higher plate count (∼2 fold increase) when compared to low power sonication. While the incorporation of OH-MWCNTs into the poly(GMA-co-EDMA) monolith acted as an amendment boosting the nonpolar character of the monolith and providing additional π-π interactions, the diol derivative monolith with its polar backbone character acted nearly as a support for the OH-MWCNT stationary phase giving rise to a carbon nanotube sorbent providing hydrophobic and π-π interactions via the incorporated OH-MWCNTs. These two kinds of columns were evaluated using alkylbenzenes, toluene derivatives, aniline compounds, phenols and polyaromatic hydrocarbons.