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Abstract

The goal of the present work is to develop simple, rapid, and sensitive extractive spectrophotometric methods for the assay of nimesulide in pharmaceutical formulations and human plasma. The methods depend on the formation of colored ion-pair complexes between nimesulide and five different reagents, bromocresol green (BCG), bromocresol purple (BCP), bromothymol blue (BTB), brilliant blue G (BBG) and methyl orange (MO) in Britton-Robinson buffer solutions of pH 2.0-3.5. The colored products were extracted in chloroform and absorbance measured at 412, 410, 407, 502 and 482 nm, respectively. The analytical parameters and their effects on the reported systems were investigated. The extracts are intensely colored and very stable at room temperature. The calibration graphs were linear over the concentration range of 2-18 μg/mL for BCG, BTB and BBG, 2-16 μg/mL for BCP and 2-14 μg/mL for MO. The stoichiometry of the reaction was found to be 1 : 1 in all cases and the conditional stability constant (K f) of the complexes were calculated. The proposed methods were successfully extended to pharmaceutical preparations in tablet form. Excipients used as additives in commercial formulations did not interfere with the analysis. The proposed methods can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of the analytical technique are of great importance.

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