Spectrophotometric analysis of mixtures of acetaminophen, salicylamide, and codeine phosphate in tablets

A simple and accurate spectrophotometric procedure for the analysis of a mixture of acetaminophen, salicylamide, and codeine phosphate is described. Determination of the first 2 components depends on pH-induced differential spectral changes of their nitroso derivatives. The third component is assayed by the acid dye method. The proposed procedure was successfully applied to the analysis of laboratory-made and commercial tablets containing the ternary drug mixture.