Fluorescence quenching and measurement of captopril in pharmaceuticals

Abstract

The mechanism of fluorescence quenching of the product S in the presence of captopril was studied. The maximum emission wavelength of the product S was at 405 nm with the excitation wavelength at 316 nm. It was found that the fluorescence quenching of product S was of a static one and the binding constant (K) was 9.29 × 106 J mol^-1. A linear relationship was found between the relative fluorescence intensity of the product S-captopril system and the concentration of captopril. Under optimum conditions, the linear range of the calibration curve for captopril was 2~160 μg L^-1 with a correlation coefficient of 0.9926 and a detection limit of 0.1 μg L^-1. The relative standard deviation (RSD) was 3.60%. The analytical results of the pharmaceuticals obtained by this novel method agreed quite well with those obtained by the KIO3 titrimetry.