Simplified GLC assay for lidocaine in plasma.

A simple, rapid GLC method for the determination of lidocaine in plasma is described. After addition of mepivacaine as an internal standard, the plasma sample is deproteinated and centrifuged. The supernate is alkalinized, and the lidocaine and internal standard are extracted into a microvolume of carbon disulfide. By using GLC with a flame-ionization detector, linear concentration-response curves were obtained in the 1-6 microgram/ml range. The method can easily determine plasma concentrations at the 250-ng/ml level when a 1-ml plasma sample is analyzed.