title: Use of guanidine hydrochloride and ammonium sulfate in comprehensive in-line sorption enrichment of xenobiotics in biological fluids by high-performance liquid chromatography.
abstract: A novel approach has been developed for direct injection of physiological fluids on an in-line extraction pre-column followed by column switching in order to introduce the adsorbed xenobiotic onto the analytical column. The physiological fluid is pre-treated with guanidinium solution in water (200 microliters of fluid plus 300 microliters of a reagent containing 8.05 M guanidinium and 1.02 M ammonium sulfate) in order to denature protein binding sites and to serve as a universal solvent for a divergent range of polar to non-polar xenobiotics in a hydrophilic medium. A 0.5 M ammonium sulfate solution (500 microliters) is used as a pre- and post-flush reagent for the extraction pre-column (30 mm x 2.1 mm I.D.). The pre-flush reagent prepares the sorbent environment of the C18 pre-column for the hydrophobic retention of analytes. The post-flush reagent flushes non-retained sample proteins and salts to waste prior to switching the pre-column in-line with the analytical column. Universal chromatographic conditions for the analytical phase allows elution of a range of polar to non-polar xenobiotics within 20 min from an end-capped C8 silica analytical column (250 mm x 4.6 mm I.D.). This is effected by a linear gradient from a binary system consisting of solvent A (0.05 M KH2PO4) and solvent B (acetonitrile-isopropanol, 80:20, v/v).
authors: Department of Pharmacology, Faculty of Medicine, University of Stellenbosch, Tygerberg, South Africa.
authors: P B
authors: PB
authors: Kruger
authors: C F
authors: CF
authors: Albrecht
authors: P P
authors: PP
authors: Van Jaarsveld
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D019791:Guanidine; D006146:Guanidines / Q000737:chemistry*; D006801:Humans; D007202:Indicators and Reagents; D062025:Organophosphate Poisoning; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D015262:Xenobiotics / Q000032:analysis*
chemical_list: D006146:Guanidines; D007202:Indicators and Reagents; D012997:Solvents; D015262:Xenobiotics; D019791:Guanidine; D000645:Ammonium Sulfate