Automated analysis of methamphetamine and amphetamine in urine using headspace - Solid phase microextraction

Abstract

An automated system for extraction and determination of methamphetamine (MA) and amphetamine (AP) in human urine was developed using headspace-solid phase microextraction (SPME) coupled with gas chromatography/mass spectrometry (GC/MS) and in-matrix derivatization. A 50-fold diluted urine, d5-MA as an internal standard, potassium carbonate, sodium chloride and ethyl chloroformate were placed into a 10 ml vial, and sealed rapidly with a silicone - septum aluminum cap, and vortexed for 10 s. MA and AP were quickly converted to the ethylformate derivatives (carbamates) in the vial. An SPME fiber was then exposed at 80 °C for 15 min in the headspace of the vial. The extracted derivatives adsorbed to the fiber were desorbed by exposing the fiber in the injection port of a GC/MS instrument. The calibration curves showed good linearity in the range of 0.25-100 μg/ml for either MA or AP in urine. This method was applied to 100 actual urine specimens and their results were compared with those by the conventional method. No interference by impurities was found, and the total time for analysis was only 30 min for each sample.