Hybrid silica polymeric monolith-based in-tube microextraction and CE for determination of bisphenol A in beverages

On-line concentration techniques in capillary electrophoresis, including stacking and sweeping, have a weak tolerance towards complex real samples. A phenyl-functionalized hybrid silica monolithic polymeric capillary column (id 530 mu m) was prepared by in-situ co-condensation of phenyltriethoxysilane (PTES) and tetraethoxysilane (TEOS). In order to enhance the stability of a monolithic column within a wide-bore capillary, a novel and simple frit-preparation method for wide-bore capillaries was first introduced by immobilizing a short length of capillary of suitable outer diameter at the end of the monolithic capillary column during condensation of the sol-gel solution. The monolithic column was used for the extraction of bisphenol A (BPA) from cola samples, and the interfering compounds can be removed from the samples with 40% ACN solution (v/v) as eluent. The pretreated samples were further concentrated and separated using large-volume stacking and sweeping micellar electrokinetic chromatography. The method was successfully applied to the determination of bisphenol A spiked in cola, yielding a detection limit of 1.8 ng/mL. Close correlation coefficients and acceptable method reproducibility were obtained for bisphenol A over a linear range of 0.005-0.200 mu g/mL.