Gas chromatographic-mass spectrometric determination of plasma and brain cocaine in mice.

A gas chromatographic-mass spectrometric method is described for the determination of cocaine in mouse plasma microsamples and brain. Cocaine and [2H3]cocaine were extracted with pentane-isopropyl alcohol (97:3, v/v), chromatographed on a (5% phenyl) methylpolysiloxane capillary column, and detected by selected-ion monitoring of electron impact generated m/z 182 and 185 fragment ions. The small sample size (50 microliters), simplicity of workup, and high response linearity (mean r = 0.9993) distinguish the method. Cocaine was found in mouse brain at approximately 5 times greater concentration than in plasma after 20 or 40 mg/kg subcutaneous doses.