Development and validation of thin-layer chromatography and high-performance thin-layer chromatography methods for the simultaneous determination of linagliptin and empagliflozin in their co-formulated dosage form

A sensitive, simple and validated thin-layer chromatography (TLC) method (method A) and a high-performance thin-layer chromatography (HPTLC) method (method B) have been developed for the simultaneous determination of linagliptin (LNG) and empagliflozin (EMP) in laboratory prepared mixtures and in their co-formulated pharmaceutical preparations. Chromatographic separation has been done using TLC silica gel 60 F254 aluminum plates (20 cm × 10 cm, 0.25 mm thickness) and the mobile phase consisting of chloroform‒methanol‒ammonia (33%) (9:1:0.1, V/V) for method A. Chromatographic separation in method B was carried out using HPTLC nano-silica gel 60 F254 glass plates (10 cm × 10 cm, 0.1 mm thickness) and the mobile phase consisting of chloroform‒methanol‒ammonia (25%) (10:1:0.1, V/V). The optimized chromatographic conditions gave good peak shapes with good resolutions at acceptable RF values of 0.25 ± 0.01 for EMP, 0.56 ± 0.01 for LNG in method A, 0.31 ± 0.01 for EMP and 0.71 ± 0.01 for LNG in method B. Both methods were validated for linearity, accuracy, precision and specificity. The calibration plots were linear over a concentration range of 0.4‒10 µg/band with a correlation coefficient of 0.9998 for EMP and 0.2‒5.0 µg/band with a correlation coefficient of 0.9998 for LNG in method A. In method B, the linear range for calibration was 0.1‒5.0 µg/band with a correlation coefficient of 0.9999 for EMP and 0.05‒2.5 µg/band with a correlation coefficient of 0.9999 for LNG. The optimized methods were successfully applied for the determination of the studied drugs in laboratory prepared mixtures and in their co-formulated pharmaceutical preparations with no significant difference observed upon statistical comparison between the proposed and reported methods.