Development and Validation of a New Analytical Method for Determination of Linagliptin in Bulk by Visible Spectrophotometer

A simple, economical and specific analytical method have been developed for determining and validation Linagliptin (LNG) in bulk. This method is based on condensation reaction between a primary amine in LNG and aldehyde group in P-Dimethylaminobenzaldehyde (PDAB) to form the yellow Schiff base with a wavelength at 407 nm. The optimum experimental conditions for the formulation of the colored complex have been studied. The optimum conditions were 1 ml of 5% w/v reagent solution with methanol and distilled water as a solvent for both PDAB, LNG respectively, also adding 2 ml of HCl as an acidic medium, heating to 70 - 75℃ on a water bath for 35 minutes. Furthermore, the stoichiometry of reaction has been studied according to Job’s and Molar ratio method which was expressing 1:1 for LNG and PDAB. The researcher modified the method. The results show that the linearity in the concentration range (5-45 µg/ml) with correlation coefficient R² = 0.9989 with percent recovery (99.46 – 100.8%) and RSD was less than 2%, LOD and LOQ 1.5815 -4.7924 μg/ml respectively. This method can show a high quality and there is no significant interference with excipients and in pharmaceutical forms. None of the studies showed a developing of this method before.