Determination of three nitroimidazoles in rabbit plasma by two-step stacking in capillary zone electrophoresis featuring sweeping and micelle to solvent stacking

This study reports a sweeping and micelle to solvent stacking (MSS) method for fast stacking of nitroimidazoles in capillary zone electrophoresis (CZE). The optimal experimental conditions are run buffer of 25   mM sodium phosphate (pH 1.5) and 0.50% (v/v) methanol, micellar solution of 30   mM sodium dodecyl sulfate, applied voltage of 28   kV, and sample and micellar solution injection of 100   s. By applying this new on-line preconcentration technique, the nitroimidazoles content can be determined within 9   min with the limit of detection ( S / N   =   3) ranging 2.3–3.0   ng/mL, which is lower than that of conventional CZE analysis. The proposed MSS technique affords 20-, 12- and 38-fold improvements in sensitivity for the detection of dimetridazole, metronidazole and secnidazole, respectively. The relative standard deviations (RSDs) of intra-day and inter-day are 2.1–3.6% and 2.7–4.6% ( n   =   6), respectively. The recoveries in pretreated rabbit plasma at spiked levels of 5.0–10.0   μg/mL are 92.0–101.1% with RSDs lower than 3.4%. The proposed sweeping and MSS-CZE is a highly sensitive method for the detection of nitroimidazoles in biological and clinical samples and has been successfully applied to analyze nitroimidazoles in pretreated rabbit plasma.