Rapid analysis of acetaminophen in serum by gas chromatography-mass spectrometry with extractive derivatization using a diatomaceous earth tube

A new analytical method for acetaminophen (ACAP) in serum was developed by modifying an existing method used for amphetamines, which used extractive derivatization followed by gas chromatographymass spectrometry. After a serum sample was adjusted to pH 12.8, it was applied onto a diatomaceous earth tube; the analyte was simultaneously extracted and heptafluorobutyrylated during elution with a solvent containing a derivatizing reagent. Three internal standard (IS) candidates were tested: N-acetyl-d ₃-paminophenol, N-acetyl-m-aminophenol, and N-acetyl-4-amino-m-cresol. All ISs gave good linear relationships (r ² > 0.999) for ACAP in the concentration range from 1 to 200μg/ml. The detection limit for ACAP using each IS was estimated to be 0.05–0.1μg/ml. Intraday precision was satisfactory with a coefficient of variation of less than 8.3%. The use of this method with any of the three ISs is recommended in forensic and clinical toxicology because of its rapidity and good reproducibility.