Spectrophotometric Determination of Some Nonsteroidal Anti-Inflammatory Drugs by Oxidative Coupling Reaction

Two simple, sensitive and rapid spectrophotometric methods have been described in the present work for the assay of non-steroidal anti-inflammatory drugs, meloxicam (MLX) and tenoxicam (TNX) in pure and pharmaceutical formulations. The methods were based on oxidative coupling of MLX [Method A] and TNX [Method B] with 3-methylbenzothiazoline-2-one hydrozone (MBTH) in presence of iron(III) chloride as an oxidant to form colored complexes. The colored complexes exhibited absorption maxima at 619 nm for method A and method B. Reaction conditions have been optimized to obtain coloured complexes of higher sensitivity and longer stability. Beer's law is obeyed in the concentration range of 0.2-10 μgml-1 and 0.1-5 μgml-1 with molar absorptivity values of 15.82x104 and 16.61x104 lmol-1cm-1, for method A and method B, respectively. The developed methods have been successfully applied to analysis of MLX and TNX in bulk samples and pharmaceutical formulations. A statistical comparison of these results with those of official or reported methods revealed good agreement and indicated no significant difference in precision.