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A method for identifying the enantiomers of N,O-di-trifluoroacetylated ephedrine (EP) and norephedrine (NE) and the enantiomers of pseudoephedrine (PEP) and pseudonorephedrine (PNE) in plasma was developed using chiral capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). N,O-Di-trifluoroacethyl (TFA) derivatization was accomplished in a dried hydrochloride extract of plasma (minimum quantity of 0.2 mL). An SIM GC-MS method with a β-cyclodextrin chiral capillary column allowed the successful and simultaneous detection of each TFA-derivatized stereoisomer of EP, NE, PEP, PNE, and an internal standard (IS; S-(+)-ethylamphetamine). Each TFA-drivatized stereoisomer was identified using four mass fragment ions (m/z 140, 154, 168, and 230). The TFA-derivatized stereoisomers of EP, NE, PEP, PNE, and IS were separated completely and were detected with sufficient sensitivity. The assay allowed the stereoisomers to be determined in a linear range of 12.5-1250 ng/mL for the EP stereoisomers and a linear range of 5-1250 ng/mL for the PEP, NE, and PNE stereoisomers. The detection limits were 7.5 ng/mL for the EP stereoisomers and 2.5 ng/mL for the PEP, NE, and PNE stereoisomers. The intra- and interday precisions were less than 5.9% and 8.2%, respectively. This chiral capillary SIM GC-MS method was sufficiently effective in the analysis of plasma from users of over-the-counter cold medicines and was also fully applicable to the plasma analysis of guinea pigs following their treatment with racemic EP.

journal of analytical toxicology.

Simultaneous Identification of the Enantiomers and Diastereomers of N,O-Di-trifluoroacetylated Ephedrine and Norephedrine in Blood Plasma using Chiral Capillary Gas Chromatography-Mass Spectrometry with Selected Ion Monitoring