Development and Validation of Stability Indicating HPTLC Method for the Determination of Metformin Hydrochloride and Benfotiamine in Bulk and Combined Dosage Form

Context: A Simple, selective, precise, and Stability indicating High Performance Thin Layer Chromatography (HPTLC) method of analysis of Metformin Hydrochloride (MET) and Benfotiamine (BENT) both as a bulk drug and in their combined formulation has been developed. Method: The basic aim of this method is to separate both the drugs by HPTLC and measure their spots at 249 nm. The separation was carried out on TLC aluminium sheets of silica gel 60F 254 using Benzene: Methanol: Triethylamine (8.5:1:0.5, v/v/v) as a mobile phase. Stability of MET and BENT was carried out by forced degradation study. Result: MET and BENT gave distinct and well defined peak at Rf 0.26 and 0.72, respectively. Calibration curves were linear in range of 500-3000 and 75-450 ng/spot for MET and BENT, respectively. Method was successively applied to tablet formulation. Stability study shows that the chromatograms of samples degraded with acid, base, hydrogen peroxide, light and dry heat showed well separated spots of pure MET and BENT as well as some additional peaks at different RF values. Conclusion: The HPTLC method was also able to selectively quantitate Metformin hydrochloride and Benfotiamine in presence of their degradation products obtained in forced degradation study. Hence, the method can be used as stability indicating. The method was validated as per ICH guidelines and it is applied for the analysis of pharmaceutical dosage form containing these two drugs.