A Simple and Environmentally Friendly Reflectometric Method for the Rapid Quantitative Analysis of Captopril in Pharmaceutical Formulations

Abstract

This paper describes a simple, environmentally friendly and rapid quantitative spot test procedure for
the determination of captopril (CPT) in bulk drug and in pharmaceutical formulations by using diffuse
reflectance spectroscopy. The proposed method is based on the reflectance measurements of the
orange compound (max 490 nm) produced by the spot test reaction between CPT and p-chloranil (CL).
Under optimal conditions, calibration curves were obtained for CPT by plotting the optical density of
the reflectance signal (AR) vs. the log of the mol L-1
concentration, from 6.91x10-3
to 1.17x10-1
, with a
good coefficient of determination (R
2
= 0.9992). The common excipients used as additives in
pharmaceuticals do not interfere in the proposed method. The method was applied to determine CPT
in commercial pharmaceutical formulations. The results obtained by the proposed method are
compared favorably with those obtained by an official procedure at 95% confidence level. The method
validation results showed that the sensitivity and selectivity of the methods were adequated for drug
monitoring in industrial quality control laboratories.