Stacking and quantitative analysis of lovastatin in urine samples by the transient moving chemical reaction boundary method in capillary electrophoresis

A simple, sensitive, and useful concentration method for lovastatin (Lvt) in urine has been developed based on the transient moving chemical reaction boundary method (tMCRBM) in capillary electrophoresis. The MCRB is formed with acidic sample buffer (Gly-HCl) and alkaline running buffer (Gly-NaOH). The following optimal conditions were determined for stacking and separation: electrophoretic buffer of 100 mM Gly- NaOH (pH 11.52), sample buffer of 20 mM Gly-HCl (pH 4.93), fused-silica capillary of 76 cm x 75-mu m i.d (67 cm from detector), sample injection at 14 mbar for 3 min. A 21- to 26-fold increase in peak height was achieved for detection of Lvt in urine under the optimal conditions compared with normal capillary zone electrophoresis. By combining the sample pretreatment procedure with the stacking method, the sensitivity of Lvt in urine was increased by 105- to 130-fold. The limits of detection (LOD) and quantification (LOQ) for Lvt in urine were decreased to 8.8 ng/mL and 29.2 ng/mL, respectively. The intra-day and inter-day precision values (expressed as RSD) were 2.23-3.61% and 4.03-5.05%, respectively. The recoveries of the analyte at three concentration levels changed from 82.65 to 100.49%.