Simple analysis of acetaminophen in human plasma by solid-phase microextraction and gas chromatography

We have developed a simple method for extraction of acetaminophen (paracetamol) in human plasma by solid-phase microextraction (SPME) using 2-acetamidophenol as internal standard (IS). After heating a vial containing a plasma sample with acetaminophen and IS at 65°C for 30 min in the presence of Na₂SO₄ and NaHCO₃ solution, a polyacrylate-coated fiber was exposed to the liquid-phase to allow adsorption of acetaminophen and IS. The fiber needle was then injected into a capillary gas chromatograph for analysis. Although the extraction efficiencies of acetaminophen were 0.12-0.13%, the calibration curve showed good linearity in the range of 2.5-200 μg/ml; intra- and inter-day assay coefficients of variation were 5.8 and 13.6% for 100 μg/ml acetaminophen, respectively. The detection limit was about 0.5 μg/ml. Acetaminophen could be actually measured by this method for plasma specimens of volunteers, who had ingested the drug. The above results show that the present SPME method is recommendable for analysis of acetaminophen in forensic toxicology and clinical pharmacology, because of its simplicity and reliability.