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Many methods have been described for the assay of paracetamol, many of them now only of historical interest. For accurate research purposes high performance liquid chromatography is favoured for its sensitivity, precision and specificity.

However, for rapid assay of paracetamol in hospital patients simple colorimetric enzyme based methods are commonly used.

For example, one popular method is based on the use of an enzyme specific for the amide bond of acylated aromatic amines. It cleaves the paracetamol molecule, yielding p-aminophenol, which reacts specifically with o-cresol in ammoniacal copper solution to produce a blue colour which can be measured with a spectrophotometer. In practice such methods are commonly automated in hospital laboratories.

Many UK hospitals participate in national external quality assessment schemes (UK NEQAS) to ensure accuracy and consistency of their laboratory assays.

For Further Information:

  1. Stewart M.J. and Watson I.D.; 1987; Analytical reviews in clinical chemistry: methods for the estimation of salicylate and paracetamol in serum, plasma and urine; Annals of Clinical Biochemistry; 24; pp552-565.

  2. Price C.P., Hammond P.M. and Scawen M.D.; 1983; Evaluation of an enzymic procedure for the measurement of acetaminophen (paracetamol); Clinical Chemistry; 29; pp358-361.