DETERMINATION OF COCAINE, NORCOCAINE, BENZOYLECGONINE AND ECGONINE METHYL-ESTER IN RAT PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

An isocratic high-performance liquid chromatographic method with ultra violet detection at 235 nm is described for the determination of cocai ne and its metabolites benzoylecgonine, norcocaine and ecgonine methyl ester in rat plasma, collected during toxicity studies. Following sim ultaneous solid-phase extraction of all analytes and the internal stan dard tropacocaine, cocaine, benzoylecgonine and norcocaine were separa ted on a C-18 column. Ecgonine methyl ester and cocaine were separated on coupled cyanopropyl and silica columns, following derivatization o f ecgonine methyl ester to p-fluorococaine. The extraction efficiencie s of these compounds from plasma ranged from 78 to 87%, while the limi ts of detection ranged from 35 to 90 ng/ml. The assay was linear from 300 to 5000 ng/ml, and the within-day precision 2 to 8% over this conc entration range.