On-fiber derivatization for direct immersion solid-phase microextraction Part I: Acylation of amphetamine with pentafluorobenzoyl chloride

On-fiber derivatization has been used for solid-phase microextraction (SPME) with gas chromatography in order to increase the extractability and detectability. Amphetamine, which has been used as a model compound, was derivatized with pentafluorobenzoyl chloride that was loaded on the fiber prior to the direct immersion of the fiber into the sample. The extraction performance of amphetamine with and without on-fiber derivatization has been compared. As the derivative possesses properties other than its parent compound, its partitioning between the polydimethylsiloxane coated fiber and sample matrix is different, i.e., with on-fiber derivatization a yield of 55% could be obtained in 55 min while without derivatization a yield of 40% has been obtained after a 105 min extraction. As the derivatization reagent is very suitable for electron capture detection, this detection system gave a factor of about 1000 better response for the derivative compared to flame ionization detection. Optimization of the method is presented for buffer solutions to show its benefits. Good linearity (r = 0.9991) for a 50 pg/mL to 5 ng/mL range has been obtained. The applicability for urine analysis has shortly been demonstrated.