Enantiomeric determination of amphetamines: Exploring a novel one-step solid-phase microextraction-based approach

The recent advances in fiber manufacturing technology, solid-phase microextraction (SPME) is now widely studied for its effectiveness for the pretreatment of various categories of samples. This study explores a novel SPME approach for enantiomeric analysis of amphetamines, in which absorption/derivatization are accomplished in one step. Specifically, (S)-(−)-N-(Trifluoroacetyl)-prolyl chloride was adopted as the chiral derivatizing reagent and added directly into the sample matrix. Analytical parameters, such as temperature, absorption/desorption duration, and the amount of derivatizing reagent, were studied to determine their effects on the yield of analytes. The derivatization products resulting from this study show excellent desorption characteristics on the polydimethylsiloxane-coated fiber adopted in this study. Optimal operational parameters (absorption: 70 °C for 10 min; injection: 250 °C for 5 min) cause minimal negative impact on the fiber, allowing repeated use of the fiber for more than 30 times. For quantitation, data were collected under selected ion monitoring (SIM) mode using m/z 237 and 251 to designate derivatized amphetamine and methamphetamine. This method was evaluated and proved to be effective in (a) quantitative determination of the enantiomeric pairs of amphetamine and methamphetamine – in terms of repeatability, linearity, and limits of detection and quantitation; and (b) generating case-specimen data comparable to those derived from a conventional Liquid–liquid extraction approach. Good linearity for the calibration curves were established in the range of 1000–50 ng/mL for both analytes. The limits of detection for these analytes were 30 ng/mL.