Polymer monoliths with silver nanoparticles-cholesterol conjugate as stationary phases for capillary liquid chromatography.

Monoliths in fused-silica capillaries were prepared by an in-situ polymerization using glycidyl methacrylate (GMA) as a functional monomer and in the presence of different crosslinkers such as ethylene dimethacrylate (EDMA), trimethylolpropane trimethacrylate (TRIM), 1,6-hexanediol dimethacrylate (HEDMA), pentaerythritol tetraacrylate (PETeA), triethylene glycol dimethacrylate (TriEDMA), while azobisisobutyronitrile (AIBN) was an initiator. The monoliths' surfaces were modified chemically with cystamine dihydrochloride, followed by immobilization of Ag-NPs the surface of which was functionalized with cholesterol cysteamine (Chol-SH). Such a new material enabled the separation of proteins in a reversed phase mode. The influence of the kind of a cross-linker and composition of the porogenic solutions on the porosity and separation properties of the obtained polymers was investigated and discussed. It was found that the amount of Ag-NPs embedded on the monoliths' surfaces depended on the porous properties of the monoliths, which was directly connected with the kind of the cross-linkers used. For the determination of the amount of the attached Ag-NPs the thermogravimetric analysis was used and additionally the ISEC method as a comparative method was also proposed. It was found that the maximum amount (about 20% by weight) of the 10nm Ag-NPs was attached to the poly(GMA-EDMA) and poly(GMA-TRIM) monoliths.

Hypercrosslinked cholesterol-based polystyrene monolithic capillary columns.

Cholesteryl methacrylate has been used to obtain hypercrosslinked poly(cholesteryl methacrylate-co-4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic stationary phase for capillary liquid chromatography. Different contents of cholesteryl methacrylate and toluene in polymerization mixture have been tested to obtain chromatographic performance. The best column has been prepared using 7% of cholesteryl methacrylate and 1% of toluene in polymerization mixture. Such a monolithic material exhibited a surface area of 452m2/g (BET). The column efficiency of about 63 000 plates/m (H=15µm) was achieved for benzene. The polystyrene column with cholesteryl methacrylate providing an additional functional group gave the highest efficiency compared to known poly(4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) and poly(cholesteryl methacrylate-co-trimethylolpropane trimethacrylate) monolithic columns. All of the above capillary columns were used for the separations of small molecules, such as alkylbenzenes, o-terphenyl/triphenylene, parabens, and proteins in reversed-phase liquid chromatography mode. The relative standard deviation of day-to-day reproducibility of hypercrosslinked poly(cholesteryl methacrylate-co-4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic columns were between 12.39-15.95% for retention factors and 10-24% for plate heights, respectively.