Validation of a gas chromatography--ion trap tandem mass spectrometry for simultaneous analyse of cocaine and its metabolites in saliva.

Cocaine (COC) is one of the most widely used drugs of abuse. Therefore numerous procedures are published in the literature to propose an analysis of this substance and related compounds in different matrixes. In the same way, the authors have described, in a previous work, the simultaneous analysis of COC and three of its metabolites in hair by gas chromatography-ion-trap tandem mass spectrometry (GC-MS/MS) using chemical ionization with isobutane. The present paper investigated the ability to transfer this convenient existing method for hair to another matrix, in occurrence saliva. The aim of this work was then to verify that the whole procedure (solid phase extraction (SPE) and analytical method) was also convenient to analyse simultaneously COC and three of its metabolites in this matrix. Therefore this sensitive GC-MS/MS method has been studied for the simultaneous analysis of COC, anhydroecgonine methylester (AEME), ecgonine methylester (EME) and cocaethylene (COET) in saliva samples. The method has been validated and its performances were evaluated in terms of trueness and precision using quality control (QC) samples. For quantification, the following ranges were found appropriate: 5-500 ng/ml for EME, 2-500 ng/ml for COC and COET; AEME could only be determined "semi-quantitatively" between 2 and 200 ng/ml according to our chosen acceptance criteria. Suggested dissociation pathways have also been proposed to interpret the obtained spectra.