Quantitative determination of amphetamine in plasma using negative ion chemical ionization GC‐MS of o‐(pentafluorobenzyl‐oxycarbonyl)‐2,3,4,5‐tetrafluorobenzoyl derivatives

Quantitative determination of amphetamine in plasma by the use of a novel electrophoric derivatization reagent, o‐(pentafluorobenzyloxycarbonyl)‐2,3,4,5‐tetrafluorobenzoyl chloride is described. Amphetamine can be quantitatively measured down to 49 pg/mL plasma using only 250 μL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionization MS. Plasma samples were made alkaline with carbonate buffer and treated with n‐hexane and reagent solution for 20 min, which, after concentration was measured by negative ion chemical ionization GC‐MS. The method is rapid as extraction and derivatization occur in one single step. ²H₅]‐Amphetamine was used as an internal standard. Validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, benchtop stability, freeze–thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.