A rapid method of determining amphetamine in plasma samples using pentafluorobenzenesulfonyl chloride and electron-capture gas chromatography.

Acute administration of (+)-amphetamine has been used as a model for mania in humans since it mimics the physiological, biochemical, and cognitive effects seen in mania. A rapid and sensitive method for the determination of amphetamine in human plasma samples using gas chromatography with electron-capture detection was developed in our laboratory to follow the time course of amphetamine levels in patients receiving this drug as part of a study using amphetamine as a model for mania. Blood samples were taken from healthy male volunteers at 30, 60, 90, 150, 210, 240, and 480 min after administration of 25 mg of (+)-amphetamine. Plasma was isolated by centrifugation and used for the analysis. This method is a modification of the procedure described by Paetsch et al. [J. Chromatogr. 573 (1992) 313] for the determination of amphetamine in rat brain tissue. Amphetamine was derivatized under basic conditions using pentafluorobenzenesulfonyl chloride (PFBSC) prior to analysis on a gas chromatograph equipped with a capillary column and an electron-capture detector. The internal standard used was benzylamine. The structure of the amphetamine derivative was confirmed using combined gas chromatography-mass spectrometry (GC-MS). The limit of detection was <1 ng/ml, and the method was linear in the 1- to 100-ng range used. Mean amphetamine levels peaked at 3.5 h after drug administration, and were 40.8 +/- 1.5 ng/ml at that time. This procedure produces a stable derivative with excellent chromatographic properties and is both simple and reproducible.