Spectrophotometric Determination of Rosiglitazone Maleate with the Reagent Congo Red

In a B-R buffer solution of pH 5.50, an ion-association complex was formed by the reaction of congo red with rosiglitazone maleate (RGM) with the molar ratio of 2 to 1, leading to decoloration of the congo red reagent, i.e., at the wavelength, 494 nm, the absorption maximum of congo red, the values of positive absorbance of the reaction system decrease with the increase of concentration of RGM, or on the other side, an increase of negative absorbance was observed. As shown by experiment. Beer′s law was obeyed in the concentration range within 7.20×10-6mol·L-1 of RGM, and the apparent molar absorptivity found was 4.75×104L·mol-1·cm-1. Value of detection limit (3s) found was 4.36×10-7mol·L-1. The proposed method was applied to the determination of RGM in RGM tablet and human urine, giving results in consistency with those obtained by HPLC. Values of recovery found were in the range of 102.7%-104.2%.