Microdetermination of nitroprusside by its inhibitory effect on the photolysis of the methylviologen-EDTA-acridine yellow system

A study of the photochemical reaction of the methylviologen (MV²⁺)-EDTA-Acridine Yellow system in the presence of nitroprusside (NP) is presented. The rate of photoreduction of methylviologen to the cation radical MV⁺ is dramatically retarded by small amounts of NP, which has an inhibitory effect on the excited state of Acridine Yellow, which is the activator of the process. Optimal conditions for the determination of NP in the range of concentrations between 2 × 10^–6 and 3 × 10^–5 M are described. The method proposed has been applied with excellent results to the determination of NP in pharmaceuticals and human serum, after protein elimination by perchloric acid.