Abstract

A simple, fast, precise and accurate liquid chromatographic method was developed for the simultaneous estimation of paracetamol, methocarbamol and diclofenac potassium in tablets. Drugs were chromatographed on a reverse phase Hypersil C18 column using a mobile phase, 25 mM phosphate buffer (pH adjusted to 7.0±0.1) and acetonitrile in the ratio of 65:35 v/v. The flow rate was 1.2 ml/min and the effluent was detected at 225 nm. Chlormezanone was used as an internal standard. The retention time of paracetamol, methocarbamol and diclofenac potassium were 2.74, 3.82 and 6.05 min, respectively. The method was linear (correlation co-efficient was more than 0.999), precise (percentage residual standard deviation for 0.15 for paracetamol, 0.17 for methocarbamol and 0.16 for diclofenac potassium), accurate (overall mean average recovery yields: 99.9% for paracetamol, 100% for methocarbamol and 101% for diclofenac potassium) and selective. Due to its simplicity and accuracy, the method was suitable for routine quality control analysis of these drugs in combined dosage form.