SIMULTANEOUS DETERMINATION OF LIDOCAINE, BUPIVACAINE AND TETRACAINE IN HUMAN PLASMA BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

A HPLC method for the determination of lidocaine, bupivacaine and tetracaine in human plasma with verapamil as internal standard has been established. This method was carried out on an ODS column using modified methanol (0.51 ml of n-butylamine and 0.3 ml of glacial acetic acid added to 300 ml of MeOH)-water (75:25) as mobile phase operated in recycling mode. The procedure is as follows: transfer 1.0 ml of plasma into a 12 ml glass centrifuge tube, add one drop of 2 N NaOH solution (if tetracaine is present, one drop of 10% sodium metabisulfite solution and 0.1 ml of 2 N NaOH solution must be added to the specimen tube before collecting the sample in order to prevent hydrolysis), add 40μ1 of the internal standard (0.16μg/μ1)and 8 ml of ethyl ether-dichloromethane (10/8,V/V). shake for 10 minutes and centrifuge for 5 minutes at 3000g. Transfer the organic phase into another tube and evaporate to dryness at 50℃. Reconstitute the residuew ith 50μl of mobile phase and inject 20μl into the chromatograph using the following conditions: column, 15×0.46 cm packed with ODS (YWG-C₁₈H₃₇, 10μm); flow rate, 1.5 ml/min; UV detector, 220 nm; range 5 mV; Chart speed, 5 mm/min.This method is simple, rapid, sensitive and has a good linearity. The absolute recoveries were found to be 101±3.6% for lidocaine, 89.3±4.1% for bupivacaine and 80±10.1% for tetracaine. Precisioin studies for both within day and day-to-day at different concentrations provided CV values of less than 10% except tetracaine which produced a CV of 10.5% for within day precision at high concentration.