Spectrophotometric determination of paracetamol in pure form and in tablets

A spectrophotometric method is proposed for the determination of paracetamol in pure form and in tablets. The method depends on reaction of the drug with ammonium molybdate in strongly acidic medium to produce molybdenum blue. Effects of variables such as temperature, heating time, acidity and reagent concentration have been evaluated to permit selection of the most advantageous technique. Beer's law was followed for concentrations of up to 6 micrograms ml-1 of paracetamol and the detection limit (p = 0.05) was 0.10 microgram ml-1. The molar absorptivity at 670 nm was 2.6 x 10(4) l mol-1 cm-1 and the relevant Sandell's sensitivity of the reaction was 0.0059 microgram cm-2 per 0.001 absorbance unit. Statistical analysis of the results and comparison with results by the BP method of analysis are also reported.