GAS-CHROMATOGRAPHY ELECTRON IONIZATION AND CHEMICAL-IONIZATION MASS-SPECTROMETRIC ANALYSIS OF URINARY PHENMETRAZINE AFTER DERIVATIZATION WITH 4-CARBETHOXYHEXAFLUOROBUTYRYL CHLORIDE - A NEW DERIVATIVE

Phenmetrazine is a central nervous system stimulant currently used as an anorectic agent. The drug is abused and is reported to cause death from overdose. We describe a new derivatization method for phenmetrazi ne using 4-carbethoxyhexafluorobutyryl chloride. Quantitation of urina ry phenmetrazine can be easily achieved by using N-ethyl amphetamine a s an internal standard. The electron ionization mass spectrum of 4-car bethoxyhexafluorobutyryl derivative of phenmetrazine showed a molecula r ion at m/z 427 and a base peak at m/z 70. In the methane chemical io nization mass spectrum, the base peak was observed at m/z 428 (protona ted molecular ion). In the electron ionization mass spectrum of 4-carb ethoxyhexafluorobutyryl derivative of the internal standard, N-ethyl a mphetamine we did not observe a molecular ion. However, in the chemica l ionization mass spectrum, the protonated molecular ion at m/z 414 wa s the base peak. The retention time of derivatized phenmetrazine (8.4 min) was substantially longer than the retention time of the underivat ized molecule. Moreover, underivatized phenmetrazine showed poor peak shape (substantial tailing) while derivatized phenmetrazine had excell ent chromatographic properties. The within-run and between-run precisi ons of the assay were 2.6% and 3.1% respectively at a urinary phenmetr azine concentration of 10 mu g/mL. The assay was linear for urinary ph enmetrazine concentration of 1 to 100 mu g/mL with a detection limit o f 0.2 mu g/mL.