Determination of methadone in urine using ion trap GC/MS in positive ion chemical ionization mode

Methadone is a potent analgesic and sedative. It is widely used in the trea tment of heroin addiction and is often encountered in forensic specimens. I n electron impact (EI) gas chromatography/mass spectrometry (GC/MS) mode, m ethadone produces predominantly a m/z 72 ion, which is not sufficiently cha racteristic for identification. Determination of the molecular ion, which c an be achieved using chemical ionization (CI) provides diagnostic informati on and better identification of the drug. This paper describes the developm ent of a positive ion CI GC/MS procedure, using a liquid reagent gas and io n trap instrumentation, for the determination of methadone and its metaboli tes in urine. CI generally produces a single molecular ion spectrum, but op timization of the reagent gas parameters increases the fragmentation of the molecule, allowing determination of ion ratios if required. The procedure is sensitive, diagnostic and is currently in routine use in our laboratory. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.