Rapid micro-method for the measurement of paracetamol in blood plasma or serum using gas-liquid chromatography with flame-ionisation detection

Abstract

A simple method for the measurement of plasma paracetamol concentrations using a novel extraction/acetylation procedure prior to gas-liquid chromatographic analysis has been developed. The sample (100 μl) is vortex-mixed for 30 sec with 0.067 mole/l phosphate buffer, pH 7.4 (50 μl), internal standard solution (N-butyryl- p-aminophenol (200 mg/l) in chloroform) (50 μl) and “acetylation reagent” (acetic anhydride-N-methylimidazole (catalyst)-chloroform, 5:1:30) (20 μl). After centrifugation at 9950 g for 3 min, a portion (5 μl) of the resulting extract is analysed on a 1.5 m × 4 mm I.D. glass column packed with 3% (w/w) C 87 hydrocarbon (Apolane-87) on Chromosorb W HP, 100–120 mesh, maintained at 235°C. A specimen together with a quality control sample can be analysed, in duplicate, within 20 min. The limit of accurate measurement of the assay is 10 mg/l, and few potential sources of interference have been identified. The method has advantages of speed and reproducibility over other gas-liquid chromatographic procedures and, in addition, of selectivity over spectrophotometric techniques. The procedure provides a useful alternative to liquid chromatographic methods for emergency paracetamol measurements.