Quantitation of cocaine and its major metabolites in human saliva using gas chromatography-positive chemical ionization-mass spectrometry (GC-PCI-MS).

An analytical method for the simultaneous determination of cocaine (COC) and its major metabolites, ecgonine methyl ester (EME) and benzoylecgonine (BEG), in saliva was developed. The method involves liquid-liquid extraction in Toxitubes A, derivatization with 99:1 (v/v) N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA)/trimethylchlorosilane (TMCS) and gas chromatography-mass spectrometry (GC-MS) determination. The detector response thus obtained is linear over the range 25-1000 ng/mL, with a reproducibility better than 93% and a recovery close to 100% for the three analytes. The limits of detection achieved were 0.9 ng/mL for EME, 2.2 ng/mL for cocaine, and 0.2 ng/mL for BEG, and the limits of quantitation were 3.0 ng/mL for EME, 7.4 ng/mL for cocaine, and 0.8 ng/mL for BEG. The proposed method was applied to 48 saliva samples from cocaine users, 96% of which were positive for the drug and/or its metabolites. Saliva is thus a suitable biological fluid for determining cocaine, EME, and BEG by GC-PCI-MS.