Simultaneous chiral impurity analysis of methamphetamine and its precursors by supercritical fluid chromatography–tandem mass spectrometry

Abstract

Impurity profiling of seized illicit methamphetamine (MA) provides information on MA manufacturing methods in clandestine laboratories, and this drug intelligence supports formulation of strategies to control MA abuse. In the present study, we developed a simultaneous chiral analysis method for MA and its precursors using supercritical fluid chromatography–tandem mass spectrometry equipped with an enantioselective stationary phase. Chromatographic conditions were optimized by systematic investigation of the flow rate, temperature, back pressure, co-solvent, additive, and mobile phase composition. The ability of the developed method was evaluated using standard and authentic illicit MA. The use of a chiral selector in the stationary phase allowed for simultaneous chiral differentiation of MA and its precursors including ephedrine, norephedrine, chloropseudoephedrine, methylephedrine, dimethylamphetamine, and amphetamine. Sufficient limit of detection, repeatability of retention time, and linearity were achieved. A switching valve interfacing a chromatograph and a mass spectrometer enabled analyzing large amounts of MA directly. The application to the authentic illicit MA samples was achieved and revealed the existence of impurities, which was not detected by conventional gas chromatography–mass spectrometry. The developed supercritical fluid chromatography–tandem mass spectrometry method could be a powerful analytical tool for MA impurity profiling.