Mass spectrometric determination of cocaine and its biologically active metabolite, norcocaine, in human urine.

A gas chromatographic mass spectrometric assay has been developed for the determination of cocaine and its pharmacologically active metabolite, norcocaine, in human urine. [2H3]Cocaine and [2H3]norcocaine were used as internal standards. The assay utilizes selective focusing to monitor in a gas chromatographic effluent the molecular ions of cocaine, [2H3]cocaine and the fragment ions of trifluoroacetylated norcocaine, [2H3]norcocaine generated by electron impact ionization. The assay can measure 2 ng ml-1 each of cocaine and norcocaine with about 5% precision. The curves, relating the amounts of cocaine and norcocaine added to control urine per 'fixed' amounts of their labeled analogs, versus the appropriate ion intensity ratios are straight lines with nearly zero intercepts and slopes of 0.98 +/- 0.01 and 0.98 +/- 0.02, respectively. The methodology is used for the analysis of urinary cocaine and norcocaine from three human subjects who received 100 mg cocaine-HCL intravenously.