Stress Degradation Studies on Simultaneous Estimation of Glipizide and Metformin Hydrochloride Using Stability –Indicating Chromatographic Methods

Two sensitive and reproducible methods are described for the quantitative determination of Glipizide and Metformin Hydrochloride in presence of its degradation products. The first method was based on high performance liquid chromatographic (LC) separation of the drug from its degradation products on the reversed phase, Cosmosil® column [C18 (5 mm, 4.6 x 150 mm, i.d.)] at ambient temperature using a buffer consisting of 10 mM potassium dihydrogen phosphate (pH adjusted to 2.5 with diluted o- phosphoric acid) and acetonitrile 50: 50 v/v as optimized mobile phase in a gradient program. The flow rate was 0.7 ml min-1 and quantitation was achieved UV determination at 225 nm based on peak area with linear calibration curves at concentration range 10-25 µg ml-1 and 20-50 µg ml-1 respectively. The second method was based on   high performance thin-layer chromatographic (HPTLC) separation followed by densitometric measurement of spots at 216 nm. The separation were carried out on Merck HPTLC aluminium sheets of silica gel 60 F 254 using Toluene: Methanol: Ethyl acetate: Formic acid in the ratio of (3:6:3:0.2, v/v/v/v), as mobile phase. This system was found to give compact spots for Glipizide and Metformin hydrochloride after double development (retention factor, RF 0.08 ± 0.02 and RF 0.74 ± 0.02 respectively). The second order polynomial regression analysis data was used forth regression line in the range of 200-1400 ng spot-1 and 200-1400 ng spot-1 respectively. Both the method has been successively applied to pharmaceutical formulation. No chromatographic interference from the tablet exicipients was found. Both the methods were validated in terms of precision, robustness, recovery, limits of detection and quantitation.