In-line solid-phase extraction-capillary zone electrophoresis for the determination of barbiturate drugs in human urine.

The abuse of barbiturate drugs is widespread, and the development of methods for their efficient separation and quantification is needed. Three barbiturate drugs were preconcentrated and determined by in-line solid-phase extraction (SPE) capillary electrophoresis (CE) in urine samples. Different parameters affecting preconcentration were evaluated, such as the sample pH, the volume of the elution plug and the sample injection time. This strategy enhanced the detection sensitivity in the range of 170- to 1840-fold, compared with normal hydrodynamic injection. The method provides limits of detection (LODs) for standard samples in the range of 0.5 to 5 ng/mL with good repeatability and reproducibility values. The LODs obtained for urine samples were in the range of 5 to 60 ng/mL. The validation with human urine samples spiked with the studied compounds demonstrated the applicability of the optimized method. This method provides a reproducible and sensitive analysis of urine samples in the determination of barbiturates drugs.