Optimization of a rapid sample pretreatment for the quantification of COC and its main metabolites in hair through a new and validated GC-MS/MS method

We developed and validated a new rapid and sensitive gas chromatography-tandem mass spectrometry method for the determination of cocaine and its metabolites benzoylecgonine, norcocaine, ecgonine methyl esther and cocaethylene in hair of consumers. Hair samples were firstly decontaminated with three subsequent dichloromethane washes, then incubated for one hour with M3® buffer to promote analytes solubilization and stabilization and finally solid phase extracted. All extracts were derivatized and injected into GC–MS/MS with electron impact ionization. Multiple Reaction Monitoring was used for the acquisition of characteristic analytes ion transitions reaching a high sensitivity 0.01 ng/mg COC and metabolites limit of quantification. The method was linear in the COC and metabolites calibration ranges (LLOQ-10 ng/mg and LLOQ-1 ng/mg, respectively). Intra-assay and inter-assay precision were always lower than 15 %, accuracy never exceeded ± 6.6 %. The main advantages of the presented method are the fast, simple and innovative pretreatment procedure together with the instrumental sensitivity that allowed to measure also less concentrated metabolites.