Efficient determination of amphetamine and methylamphetamine in human urine using electro-enhanced single-drop microextraction with in-drop derivatization and gas chromatography.

An efficient method for the determination of amphetamine (AM) and methylamphetamine (MA) using electro-enhanced single-drop microextraction (EE-SDME) and gas chromatography has been developed. One advantage of this method is that the extraction efficiency is greatly enhanced by the electric field acceleration of the mass transfer of target analytes from the sample solution to the organic solvent drop. In addition, the extracted analytes were in situ derivatized with isobutyl chloroformate (IBCF) in the droplet, which further improved the sensitivity of this method. Under the optimum conditions, the enrichment factors (EFs) for AM and MA were 247 and 782, respectively. The proposed method exhibited low limits of detection (0.27 μg/L for AM and 0.14 μg/L for MA) and good linearity over the concentration range between 1 and 2000 μg/L with regression coefficients (r) of more than 0.99. The intra- and interday recoveries were from 89.6 to 96.2% and 82.7-90.5%, respectively, and the intra- and interday precisions (RSDs) were from 5.2 to 8.3% and 8.9-12.8%. The proposed method was applied to the determination of amphetamines in a urine sample.