Determination of stimulants using gas chromatography/high-resolution time-of-flight mass spectrometry and a soft ionization source.

RATIONALE: The aim of this study was to investigate the mass spectral fragmentation of a small set of stimulants in a high-resolution time-of-flight mass spectrometer equipped with a soft ionization source using vacuum ultraviolet (VUV) photons emitted from different plasma gases. It was postulated that the use of a plasma gas such as Xe, which emits photons at a lower energy than Kr or Ar, would lead to softer ionization of the test compounds, and thus to less fragmentation. METHODS: A set of nine stimulants: cocaine, codeine, nicotine, methadone, phenmetrazine, pentylenetetrazole, niketamide, fencamfamine, and caffeine, was analyzed by gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) in positive ion mode with this soft ionization source, using either Xe, Kr, or Ar as plasma gases. Working solutions of the test compounds at 0.1 to 100 ng/µL were used to establish instrument sensitivity and linearity. RESULTS: All test compounds, except methadone and pentylenetetrazole, exhibited strong molecular ions and no fragmentation with Xe-microplasma photoionization (MPPI). Methadone exhibited significant fragmentation not only with Xe, but also with Kr and Ar, and pentylenetetrazole could not be ionized with Xe, probably because its ionization energy is above 8.44 eV. The Kr- and Ar-MPPI mass spectra of the test compounds showed that the relative intensity of the molecular ion decreased as the photon energy increased. CONCLUSIONS: When coupled to a TOF mass spectrometer this soft ionization source has demonstrated signal-to-noise (S/N) ratios from 7 to 730 at 100 pg per injection (depending on the compound), and a dynamic range of three orders of magnitude (100 pg to 100 ng) for some of the test compounds.

Determination of Phenmetrazine in urine by gas chromatography-mass spectrometry.

A sensitive and simple gas chromatographic--mass spectrometric method is described for the determination of the central nervous system (CNS) stimulant phenmetrazine in urine. The extraction and derivatization were combined into a single step with isooctane and methyl chloroformate. The limit of quantitation was 0.05 micrograms/mliters urine, and the method was linear up to 100 micrograms/mliters. The coefficients of variation (CV) for within-day runs were 1.2% and 2.4% (n = 5) for two controls containing 1.0 micrograms/mliters and 50 micrograms/mliters, respectively. During a six-month period, the same controls showed CVs of 9.1% and 8.7%, respectively (n = 40), indicating a somewhat lower between-run precision. Phenmetrazine was present in 83 out of 3000 urine samples that were screened for CNS stimulants during this period, and the concentrations ranged from 0.5-370 micrograms/mliters.

Comparative gas chromatographic analysis of narcotics. III. Phenmetrazine hydrochloride.

Chemical signatures of phenmetrazine hydrochloride were studied by gas chromatography. The inter-batch variations of the signatures were found to be large whereas the intra-batch variations were usually small. The method is used for the tracing of seized phenmetrazine hydrochloride samples to common sources, which in turn may permit further tracing back to chains of illicit distribution of this drug. The applicability of the method to other narcotics is also discussed.