IDENTIFICATION OF METHAMPHETAMINES AND OVER-THE-COUNTER SYMPATHOMETIC AMINES BY FULL-SCAN GC-ION TRAP MS WITH ELECTRON-IMPACT AND CHEMICAL IONIZATION

An underlvatized methane chemical ionization (CI) assay for measuring amphetamines in urine was evaluated against derlvatized electron impact (El) assays using a gas chromato-graph-ion trap mass spectrometer. The full-scan Cl mass spectra of methamphetamlne, ephedrine/pseudoephedrlne, and phentermlne were compared with the full scan and three-ion El mass spectra of heptafluorobutyrlc anhydride (HFBA) and 4-carbethoxyhexafluorobutyryl chloride (CB) derivatives. The fragmentation patterns for these compounds were nearly identical for the three major high molecular weight ions (m/z 254, 210, and 169 for EI-HFBA derivatives, and m/z 308, 262, and 280 for EI-CB derivatives)9 The CI mass spectra of the underivatlzed drugs contained more discernible differences at the higher molecular weights, Including m/z 119, 148, and 150 for methamphetamlne, 148, 166, and 176 for ephedrlne/pseudoephedrine, and 91, 133, and 150 for phentermine. The within-run precision ranged from 7-9% for Cl versus 5-6% for El with HFBA derivatlzation (mean 500 ng/mL, n = 5). The limits of detection (LOD) for amphetamine and methamphetamlne were 2.4 and 8.6 ng/mL, respectively, for CI versus 0.7 and 1.4 ng/mL for El. The limits of quantltatlon (LOQ) were 4.5 and 19.1 ng/mL for Cl versus 1.4 and 5.7 ng/mL for El. The use of full-scan mass spectral analysis with either electron impact or chemical Ionization provides additional qualitative data that may be helpful for measuring methamphetamlne In the presence of other sympathomlmetic amines. © 1992, Oxford University Press. All rights reserved.