Determination of Methamphetamine and Amphetamine in Urine by Headspace Gas Chromatography/Mass Spectrometry

The sensitivity of combined headspace gas chromatography (HSGC) and mass spectrometry (MS) for a stimulant (methamphetamine) and its urinary metabolite (amphetamine) was investigated. The analytical methods consisted of a combination of (1) HSGC and electron impact (EI)-MS, (2) HSGC, on-column trifluoroacetyl (TFA) derivatization of stimulants and EI-MS and (3) HSGC and chemical ionization (CI)-MS using isobutane as a reagent gas. The combination of HSGC and EI-MS after on-line TFA-derivatization of stimulants (2) was the most informative method in these three procedure, but HSGC/CI-MS (3) was the most sensitive method. Detection limits of methamphetamine (MA) and amphetamine (AP) in urine by HSGC/CI-MS were found to be about 10ng/ml (S/N>10) by monitoring quasimolecular ions of these compounds; m/z 150 and 136 observed on their mass spectra, respectively. Furthermore, the most sensitive CI-MS method was applied to quantivative analysis of these drugs excreted in urine by the selected ion monitoring (HSGC/CI-SIM).