Characterization of lidocaine and its metabolites in human plasma using capillary electrophoresis

A method for the separation of lidocaine and six of its metabolites in plas ma has been developed. Separation was performed using a buffer consisting o f 35 mM phosphate/Tris pH 3.0, 6 mM cetyltrimetylammoniumbromid (CTAB) and 9% (v/v) methanol. The key variables, CTAB and methanol concentrations, wer e optimized by the application of a factorial design. Rinsing the capillari es with ethanol between runs resulted in highly reproducible migration time s, relative standard deviation 0.69%. Under the conditions applied, the sev en analytes could be separated with high efficiency and resolution within 8 .1 min. Overall performance, as demonstrated in validation experiments, was excellent. (C) 1999 John Wiley & Sons, Inc.