Immunological screening of drugs of abuse and gas chromatographic mass spectrometric confirmation of opiates and cocaine in hair

The work presents an analytical strategy to detect drugs of abuse in hair. It involves two sequential steps: a screening by a simple enzyme-linked imm unosorbent assay (ELISA) methodology to detect opiates, cocaine and its met abolites, and benzodiacepines, followed by confirmation of opiates and coca ine metabolites in positive samples by gas chromatography coupled to mass s pectrometry (GC-MS). In the same GC-MS run other drugs for substitution the rapy (e.g. methadone and its main metabolite) can also be detected. After a double washing of hair samples with dichloromethane, hair specimens were c ut into small pieces and 10 mg samples were incubated in 2 mi of methanol-t rifluoroacetic acid (9:1) mixture, overnight at 37 degrees C. Aliquots of t he extract were then evaporated, reconstituted in buffer and analysed accor ding to the ELISA procedure. Confirmation involved solid-phase extraction o f another fraction of the extract kept at -20 degrees C, derivatization wit h heptafluorobutyric anhydride and hexafluoroisopropanol and detection of c ocaine, benzoylecgonine, ecgonine methylester, cocaethylene, morphine, code ine, 6-monoacetylmorphine, methadone and 2-ethylidene-1,5-dimethyl-3,3-diph enylpirrolidine (methadone metabolite) by selective ion monitoring after ga s chromatographic separation. During the development of the method it was v erified that no more than 10% of cocaine, opiates and benzodiacepines were lost when dichloromethane was used to wash real samples. The results also c onfirmed the increase of extractability power of TFA when it was added to m ethanol: the recovery for the analytes (cocaine and its metabolites and opi ates) added to methanol-TFA alone was of the order of 90% except for benzoy lecgonine (75%), and the recovery for the analytes added to methanol-TFA ex tract of drug-free hair was about 90% for all analytes except for benzoylec gonine and 6-MAM (around 70%). Regarding the stability of labile compounds, only small amounts of ecgonine methylester (2.3%) and morphine (7.2%) were produced, from cocaine and 6-MAM respectively, after the whole extraction procedure and two weeks of storage of methanol-TFA extracts at -20 degrees C. Satisfactory results were obtained when the procedures were applied to t he analysis of external proficency testing hair samples and actual specimen s from drug addicts. (C) 1999 Elsevier Science B.V. All rights reserved.