ABSTRACT A novel and reliable high‐performance liquid chromatography coupled with photodiode array (HPLC‐PDA) detection method was developed and validated for the simultaneous determination of metformin hydrochloride, its related impurity cyanoguanidine, and five co‐formulated antidiabetic agents—linagliptin, vildagliptin, sitagliptin, empagliflozin, and dapagliflozin—in pharmaceutical dosage forms. Chromatographic separation was achieved on a PerkinElmer Analytical Cyano column (150 × 4.6 mm, 5 µm) using a gradient elution of 15 mM orthophosphoric acid (containing 5 mM sodium heptane sulfonate) and acetonitrile at a flow rate of 1.0 mL/min. The detection wavelengths were set individually for each analyte (205–228 nm) using a PDA detector. The method was validated according to the International Council for Harmonization Q2(R2) guideline. Linearity was demonstrated within the ranges of 100–600 µg/mL for metformin, 0.2–1.0 µg/mL for cyanoguanidine, 0.25–1.25 µg/mL for linagliptin, 5–30 µg/mL for vildagliptin, 5–30 µg/mL for sitagliptin, and 0.5–3.0 µg/mL for both empagliflozin and dapagliflozin, with correlation coefficients (R 2 ) greater than 0.99. Recovery values were between 98% and 102%, and the percentage relative standard deviation values were below 2%, confirming the accuracy, precision, and overall analytical performance. No interference was observed from excipients or blank matrices, and robustness tests confirmed the method's stability under slight variations in analytical conditions. The proposed method was successfully applied to the analysis of commercial formulations, demonstrating its suitability for routine quality control and stability testing of metformin‐containing products and their fixed‐dose combinations with dipeptidyl peptidase‐4 and sodium‐glucose cotransporter‐2 inhibitors.
Bayrak et al. (Thu,) studied this question.