Detection and quantitation of amphetamine and methamphetamine: electron impact and chemical ionization with ammonia--comparative investigation on Shimadzu QP 5000 GC-MS system.

Gas chromatographic-mass spectrometric (GC-MS) analyses of amphetamine and methamphetamine with chemical ionization (CI) (NH3) and electron impact (EI) were compared after solid-phase extraction from urine. The optimal CI (NH3) conditions for amphetamines were selected; the CI mass spectra of amphetamine, methamphetamine, methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), and methylenedioxyethylamphetamine (MDEA) were obtained. Amphetamine and methamphetamine were monitored as [M+H]+ ions in SIM mode. Under these conditions the GC-MS limits of detection and quantitation were determined for amphetamine (2.1 and 5.0 mg/L, respectively) and for methamphetamine (0.9 and 2.0 mg/L, respectively). The heptafluorobutanoyl (HFB) derivatives were used to increase the sensitivity of the GC-MS analysis of amphetamines. Under CI (NH3) conditions these compounds form mainly the cluster ions [M+NH4]+. For HFB-derivatives the limits of detection and quantitation for CI (NH3) were 95 and 170 micrograms/L, respectively, for amphetamine (m/z 349) and 90 and 160 micrograms/L, respectively, for methamphetamine (m/z 363). For EI they were 10 and 30 micrograms/L, respectively, for amphetamine (m/z 240) and 9 and 27 micrograms/L, respectively, for methamphetamine (m/z 254). The GC-MS-CI (NH3) technique was found to be suitable for confirmation of amphetamine and methamphetamine in urine samples in addition to the routine GC-MS-EI method.