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SPECTROPHOTOMETRIC METHOD FOR LISINOPRIL DETERMINATION USING NINHYDRIN

LAURA SBÂRCEA^1*, LUCREŢIA UDRESCU², LIANA DRĂGAN¹, CRISTINA TRANDAFIRESCU¹, ZOLTÁN SZABADAI², MARIUS BOJIŢĂ³

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This paper presents a sensitive, accurate and rapid method for quantitative determination of lisinopril dihidrate (LIS) in bulk and pharmaceutical formulations based on the reaction with ninhydrin in the presence of potassium hydroxide. The reaction quantitatively proceeds at a temperature of 95 ± 2ºC, in 10 min and the end product, purple coloured, exhibits maximum absorption at 567 nm. The Lambert-Beer law is obayed within the range of 10 – 30 μg/mL, while the calibration curve is described by the regression equation A = 0.0312 C (μg/mL) – 0.2262, having a correlation coefficient of R2 = 0.9981 (n = 8). The influence of temperature, heating time and reactive concentrations on the end product was also analyzed, so as to render the optimal conditions for reaction. In order to validate the method, the linearity, the limit of detection (LOD), limit of quantification (LOQ), sensitivity, selectivity, precision, accuracy and recovery were determined according to ICH guidelines. The LOD and LOQ values were calculated to be 1.16 μg/mL and 3.52 μg/mL respectively. Intra-day and inter-day accuracy expressed as relative error was less than 1.12% with precision quantified as relative standard deviation ranging from 1.14 to 1.98%. The percent recovery ranged from 98.12 to 102.57%. No interferences from the common excipients were detected and therefore the method was considered specific. The proposed method was successfully applied for the quantitative determination of lisinopril from three pharmaceutical products, namely Lisigamma®, Lisinopril® Sandoz and Ranolip®.