GC–MS determination of amphetamines in serum using on-line trifluoroacetylation

An extraction and determination method of most important amphetamine derivatives in serum has been developed. The procedure comprises liquid–liquid extraction with tert-butyl methyl ether of the sample under basic conditions, centrifugation, formation of hydrochloric salts after the separation of organic phase, vacuum evaporation of the organic solvent at 60 °C, and trifluoroacetylation by on-line flash injection with MBTFA. GC analysis was performed by electron impact GC–MS in SIM mode. In this way satisfactory identification of 12 amphetamine derivatives could be obtained. Amphetamine, methamphetamine, MDA, MDMA and MDEA could be analyzed by using pentadeuterated analogs as internal standards. Low limits of detection 2.5–6.9 ng/mL could be reached. The assay was linear within the 5–100 ng/mL range with a regression coefficient greater than 0.999 for each compound. Our derivatization method is of low cost since only 1 μL of MBTFA is used for each flash trifluoroacetylation.