Determination of plasma cocaine and ethylcocaine (cocaethylene) in mice using gas chromatography-mass spectrometry and deuterated internal standards.

A gas chromatographic-mass spectrometric method is described for the determination of cocaine and ethylcocaine (cocaethylene) from mouse plasma microsamples (50 microliters). [2H3]Cocaine and [2H5]ethylcocaine served as internal standards, analytical separations were performed on a (5% phenyl)methylpolysiloxane capillary column, and detection was by selected-ion monitoring of electron-impact generated fragment ions [M - CO2Ph]. Pilot study plasma concentrations of ethylcocaine following coadministration of cocaine and ethanol were less than 5% of the parent drug.