UV–Second Derivative Spectrophotometric and Colorimetric Methods for the Determination, Validation and Thermogravimetric Analysis of New Oral Antidiabetic Pioglitazone in Pure and Pharmaceutical Preparations

Abstract

Three rapid, sensitive, and simple spectrophotometric methods have been developed for the determination of pioglitazone in pure and pharmaceutical preparations. For the first method, UV-spectrophotometry, standard solutions were measured at 270.2 nm. The first method was linear from 5.0–20.0 µgmL−1. The linearity was found to be 5.0–20.0 µgmL−1. For the second method, the distances between two extremum values (peak-to-peak amplitudes), 272.0 and 287.4 nm were measured in the second order derivative-spectra of standard solutions. Calibration curves were constructed by plotting d2 A/dλ2 values against concentrations, 2.0–12.0 µgmL−1 of pioglitazone standards in acetonitrile. The detection limits of pioglitazone were 0.10 and 0.16 µgmL−1 for UV and derivative spectrophotometric methods, respectively. The third method was based on the formation of an ion association complex with bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), and bromothymol blue (BTB). The assay was linear over the concentration range of 20.0–100.0 µgmL−1 for BCG, 10.0–100.0 µgmL−1 for BCP, 20.0–120.0 µgmL−1 for BPB, and 10.0–100.0 µgmL−1 for BTB. The detection limits of pioglitazone was found to be 0.14 µg mL−1 for BCG, 0.32 for BCP, 1.24 µgmL−1 for BPB, and 0.22 µgmL−1 for BTB. The thermal analysis of the pioglitazone was studied by Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) techniques. Enthalpy change of pioglitazone was found to be 85.16 J/g. The proposed methods were validated according to the ICH guidelines (1996) with respect to specificity, linearity, limits of detection and quantification, accuracy, precision, and robustness. The results demonstrated that the procedure is accurate, precise, specific, and reproducible (percent relative standard deviation <2%), while being simple and less time consuming. The three proposed methods have been successfully applied to the assay of pioglitazone in pure and in pharmaceutical preparations. The results compared with those obtained by an ultraviolet spectrophotometric method using t and F tests.