Gas chromatographic determination of cocaine and its metabolites in blood and urine from cocaine users in northwestern Spain

A gas chromatographic method with fl ame ionization detection (GC/FID) was developed for the determination of cocaine and its metabolites in blood and urine samples from cocaine users in Northwestern Spain. After a solid-phase extraction with Bond Elut Certify cartridges and a derivatization with bis-trimethylsilyltrifluoroacetamide-trimethylchlorosilane (1%), calibration curves were constructed over 0.4-4 micro g ml(-1) for urine and 0.1-2 micro g ml(-1) for blood, using proadifen as the reference compound. The average extraction recoveries were 75% for urine and 78% for blood. The limits of detection and quantitation were 0.071 and 0.24 micro g ml(-1), respectively. Coefficients of variation were <10% and accuracy was within +/-12%. The average blood concentrations of cocaine, benzoylecgonine and ecgonine methyl ester in 42 living patients were 0.22, 1.43 and 0.16 micro g ml(-1), respectively. Urine samples were collected from individuals in the criminal justice system (70 cases), from drug abusers admitted to emergency rooms (36 cases) and from patients under detoxification treatment (36 cases). The second group exhibited the highest average concentrations (e.g. 0.97 micro g ml(-1) for cocaine, 5.23 micro g ml(-1) for benzoylecgonine and 0.39 micro g ml(-1) for ecgonine methyl ester). Sixty- five fatal intoxications due to cocaine alone or in combination with other drugs were studied, and average blood levels were found to be higher in the deaths related to cocaine alone (e.g. 0.40 micro g ml(-1) for cocaine, 2.38 micro g ml(-1) for benzoylecgonine and 0.38 micro g ml(-1) for ecgonine methyl ester).