Abstract
Selective, linear (coefficient of linear correlation = 0.999) and accurate HPLC method for evaluation of stability of benazepril (BEN) in solid phase has been applied. Liquid chromatography was performed with a column Hypersil MOS (5 µm particle size, 250 mm × 4 mm, Merck), the mobile phase used was mixture of acetonitrile–phosphate buffer (50:50 v/v), flow rate of 1.1 mL/min, and internal standard: cetirizine dichloride (methanolic solution 0.3 mg/mL). The effluent was monitored on a UV detector at 215 nm. The influence of humidity and temperature on the stability of BEN in solid phase has been studied. The thermodynamic parameters, at 293 K of degradation of BEN hydrochloride in solid phase, E a (kJ/mol) = 121.16 ± 15.7, ΔH ≠(kJ/mol) = 118.67 ± 15.7, ΔS ≠ [J/(K × mol)] = −28.99 ± 44.5 for RH = 76.4% and E a (kJ/mol)= 85.2 ± 15.9, ΔH ≠ (kJ/mol) = 82.7 ± 15.9, ΔS ≠ [J/(K × mol)]= −139.2 ± 41.3 for RH = 0% have been calculated.
Acknowledgments
The author wishes to thank Novartis International Pharmaceutical Ltd for supplying benazepril hydrochloride (CIBACEN) pure substance. This study was financially supported by the grant no. 501‐3‐05‐05.