HPCE determination of R(+) and S(-) mepivacaine in human serum using a derivatized cyclodextrin and ultraviolet detection.

A high performance capillary electrophoresis assay for the quantitative determination of R(+) and S(-) mepivacaine in human serum is reported using heptakis (2,6-di-O-methyl) beta-cyclodextrin as the chiral selector for the separation of the enantiomers. The background electrolyte was a 100 mM phosphate buffer (pH 2.5) containing 20 mM heptakis (2,6-di-O-methyl) beta-cyclodextrin and 30 nM hexadecyltrimethylammonium bromide (HTAB). A 72 cm uncoated fused silica capillary was used for the analysis. HTAB was used as the buffer additive to decrease the adsorption of endogenous substances onto the silica wall. To separate the analytes of interest from the endogenous serum substances, a liquid-liquid extraction procedure was used. The extraction recoveries were greater than 70% for both R(+) and S(-) mepivacaine. The detection limits were around 150 ng ml-1 using 1 ml of serum and the limits of quantitation were 200 ng ml-1. The calibration curves were linear over a range of 200-2000 ng ml-1 with R(-) prilocaine as internal standard (IS) and coefficients of determination were greater than 0.999 (n=3). Precision and accuracy of the method were 4.1-7.2 and 2.6-5.9%, respectively, for R(+) mepivacaine and 4.0-7.4 and 3.2-7.4% for respectively, for S(-) mepivacaine. The HPCE method was compared to an existing HPLC method in terms of sensitivity and selectivity for the routine analysis of the drugs.