Spectrophotometric Determination of Glimepiride in Pure and Pharmaceutical Formulations Using Bromophenol Blue and Thymol Blue

Abstract

Two simple, direct and accurate spectrophotometric methods have been developed for the determination of Glimepiride (GLM) in pure and pharmaceutical formulations by ion-pair complexes with Bromophenol Blue (BPB) and Thymol Blue (TB). The methods involve the formation of yellow ion-pair complexes between BPB and TB with GLM at pH<3.8; after reacting GLM with Na2CO3 to give C24H33N4H+O5NaS which is prepared in chloroform. The formed complexes [GLM]:[BPB] in chloroform and [GLM]:[TB]2 in acetonitrile were measured at ?max 424 and 392 nm, respectively. Molar absorptivity(?) for complexes were 23000 and 28000 L.mol-1.cm-1, respectively. Beer’s law was obeyed in the concentration range of 1.126 – 46.608 ?g.mL-1 with relative standard deviations (RSD) 3.8% in presence of 5.0x10-4 mol.L-1 of BPB and 0.319 – 34.343 ?g.mL-1 with RSD 4.0% in presence of 2.5x10-4 mol.L-1 of TB. The proposed method was validated for specificity, linearity, precision, accuracy, repeatability, sensitivity (LOD and LOQ) and robustness. The results for the determination of GLM using TB were more sensitive and accurate than using BPB. The developed method is applicable for the determination of GLM in pure and different dosage forms with average assay of 99.0 to 101.0% and the results are in good agreement with those obtained by the RP-HPLC reference method.