HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC AND SPECTROPHOTOMETRIC DETERMINATIONS OF PIOGLITAZONE-HCl EITHER ALONE OR IN COMBINATION WITH METFORMIN-HCl

HPLC and spectrophotometric methods are described for pioglitazone-HCl determination in bulk powder and the dosage forms either alone or combined with metformin-HCl. The chromatographic method involves separation of pioglitazone-HCl and metformin-HCl on a monolithic column, using mobile phase of MeOH and 25 mM KH2PO4 at pH 4.9 in ratio of 75: 25 (v/v) at flow rate of 2.7 mLmin(-1), at 25 degrees C, and at 210 nm. Total elution time is less than one minute. The method is validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, and robustness. Robustness is studied for small changes in pH, flow rate, \% of MeOH, and injection volume. Limits of detection are 0.5 and 0.25 mu gmL(-1) for them, respectively. Recovery values of this method are between 97\% and 103\% and reproducibility values are within 0.99 for pioglitazone-HCl and 1.5 for metformin-HCl. Spectrophotometric method is based on oxidation of pioglitazone-HCl with excess n-bromosuccinimide followed by oxidation of metol through unreacted amount of n-bromosuccinimide and then coupling between oxidation product of metol and sulphanilic acid. Metformin-HCl does not interfere with this method. The colored compound developed in acidic medium was measured at 520 nm. Beer's law is obeyed in the concentration range of 5-20 mu gmL(-1).