Validated Spectrophotometric Methods for the Determination of Nabumetone in Tablets Dosage Form Using Three Dinitrobenzene Reagents

Three spectrophotometric methods have been described for the determination of nabumetone (NAB) in its tablets dosage form. The methods are based on the reaction of nabumetone with three dinitrobenzene reagents, namely, m-dinitrobenzene (DNB), 1-chloro-2,4-dinitrobenzene (CDNB) and 1-fluoro-2,4-dinitrobenzene (FDNB) in alkaline medium (alcoholic potassium hydroxide solution). The studied reactions depend on the tendency of these dinitrobenzene reagents to react with the active methylene adjacent to the carbonyl group of the drug. Illustrative proposed pathways showing the reaction of NAB with the three dinitrobenzene reagents were presented. Spectrophotometric measurements were achieved by recording the absorbances at 580, 573 and 574 nm for the reaction with DNB, CDNB and FDNB respectively. Different experimental parameters affecting development and stability of the produced colors were optimized. The three methods were validated with respect to linearity, ranges, precision, accuracy and limits of detection and quantification. Beer’s law was obeyed in the concentration ranges of 2-10, 40-240 and 10-50 µg/mL for DNB, CDNB and FDNB methods respectively with correlation coefficient values not less than 0.9994. In addition, detection limits of NAB were 0.27, 8.54 and 2.04 µg/mL for DNB, CDNB and FDNB methods, respectively. The proposed methods were successfully applied for assay of the drug in its tablets dosage form. Recovery data obtained by the proposed methods were favorably compared with those obtained by a reported spectrophotometric method.