Determination of lidocaine and active metabolites in blood serum by liquid chromatography with electrochemical detection.

Oxidation of lidocaine and its principal metabolites, monoethylglycine xylidide and glycine xylidide, at glassy carbon electrodes was employed to permit electrochemical detection of these compounds following separation by high-performance liquid chromatography. The absolute detection limits found for these compounds were 2 ng, 5 ng, and 4 ng injected, respectively. The resulting assay was suitable for the routine quantitation of lidocaine and these metabolites in blood serum over the entire therapeutic range, 1-6 micrograms/ml. Total analysis time is 10-15 min.