Simultaneous Spectrophotometric Estimation of Valdecoxib and Paracetamol in Tablet Formulations

The validated method was applied for determination of residual solvents in certain film-coated marketed antibiotic formulation of ciprofloxacin, norfloxacin, pefloxacin, and ofloxacin. Twenty tablets each containing 500 mg, 400 mg, 400 mg, and 200 mg of ciprofloxacin, norfloxacin, pefloxacin, and ofloxacin, respectively were accurately weighed separately. The tablets were crushed in a separate glass mortar into a fine powder, transferred into a stoppered conical flask, and extracted with 100 ml portion of dimethyl sulfoxide. The extract was filtered with Whatman filter paper No. 1 into a clean, dry 100 ml volumetric flask to get sample stock solution. A volume of 2 ml of the sample stock solution was diluted to 10 ml using dimethyl sulfoxide. From the filtered solution, 5 μl was injected into the gas chromatograph. Methylene chloride peak was detected at 5.4 min in the chromatograms of sample ciprofloxacin, norfloxacin, pefloxacin, and ofloxacin. Based on the peak areas recorded in the chromatograms, the amounts of organic volatile impurity present in the samples were calculated. Methylene chloride was found to be in the concentration range of 0.001 to 0.003 mg per tablet, which was well within the permissible limit of 600 ppm as required by the specification of ICH. The amounts of residual solvents found in the marketed formulations have been presented in Table 1.