Hypercrosslinked cholesterol-based polystyrene monolithic capillary columns

Abstract

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.