The multi-concentration and two-dimensional capillary electrophoresis method for the analysis of drugs in urine samples

A novel method has been developed by integration of multi-concentration and two-dimensional (2D) capillary electrophoresis (CE) for simultaneous enhancement of detection sensitivity and separation power in complex samples. Capillary zone electrophoresis (CZE) was used as the first dimension separation according to mobilities, from which the effluent fractions were further analyzed by micellar electrokinetic capillary chromatography (MEKC) acting as the second dimension. Cation-selective exhaustive injection (CSEI) preconcentration method was used to introduce more analytes into the capillary. Furthermore, pH junction and sweeping dual concentration strategies were employed to avoid sample zone diffusion at the interface. The resulting electrophoregram was quite different from that of either CZE or MEKC separation. Up to (0.5-1.2) x 10(4) fold improvements in sensitivity were obtained relative to the conventional electrokinetic injection method. The proposed method was successfully applied to the determination of drugs in human urine.