Quantitation of cocaine, benzoylecgonine, ecgonine methyl ester, and cocaethylene in urine and blood using gas chromatography-mass spectrometry (GC-MS).

Cocaine, a stimulant, is a commonly abused drug. Cocaine and its metabolites are measured in various biological specimens for clinical and forensic purposes. Urine or plasma or serum is spiked with deuterated internal standards cocaine-d3, benzoylecgonine-d3, ecgonine methyl ester-d3, and cocaethylene-d3 and buffered with phosphate buffer. The drugs in the sample are extracted by cation-exchange solid phase extraction. The drugs from the solid phase cartridge are eluted and the eluent is dried under the stream of nitrogen. The residue is incubated with pentafluoropropionic acid anhydride and pentafluoropropanol to form pentafluoropropionyl derivatives of ecgonine methyl ester and benzoylecgonine. Cocaine and cocaethylene are refractory to derivatization. The extract is dried, reconstituted in ethyl acetate, and injected into gas chromatography mass-spectrometry analyzer. Quantitation of the drugs in the samples is made, using selected ion monitoring, from a 3-point calibration curve.