Liquid chromatographic analysis of local anesthetics in human plasma after sample preparation by on-line dialysis. Optimization by use of experimental design

Strategy for the development of automated methods involving dialysis and trace enrichment as on-line sample preparation for the determination of basic drugs in plasma by liquid chromatography

Among the sample preparation techniques, dialysis followed by clean-up and enrichment of the dialysate on a pre-column has proved to be a useful approach for the LC determination of drugs in plasma. By use of sample processors, like the ASTED system, such bioanalytical methods can be fully automated, the dialysis and trace enrichment steps being directly coupled to LC. In order to facilitate the development of such automated methods, a strategy based on a decision tree has been elaborated. After the selection of appropriate conditions for the LC analysis, the decision tree provides information about suggested starting conditions and guidelines for the optimisation of the most important parameters likely to influence analyte recovery and method selectivity. The plasma samples are dialysed on a cellulose acetate membrane in the static-pulsed mode and the dialysate is enriched on a trace enrichment pre-column packed with octadecyl silica or with a strong cation-exchange material. This decision tree is until now restricted to the analysis of basic drugs in plasma. In order to demonstrate the applicability of this method development strategy, an automated procedure based on the coupling of dialysis with trace enrichment has been developed for the LC determination of antifungal agents (clotrimazole, econazole and miconazole) in plasma.