Computerised compensation method for the spectrophotometric determination of a single substance in the presence of interferences

Abstract

The difference curves obtained using the compensation method for the spectrophotometric determination of a single substance in the presence of interferences were computed using a BASIC computer program. The exact balance-point (end-point) was defined on a plotter. When the absorption characteristics of the substance to be determined disappear, the resulting curve corresponds to the interferences, and the concentration of the substance in the sample solution is equal to that in the reference solution. The applicability of the method was illustrated by the determination of atropine sulphate in an injection solution and ephedrine hydrochloride and nadolol in tablets. The results showed good agreement with those obtained using the experimental compensation method and a second-derivative ultraviolet spectrophotometric method.