A polarographic and voltammetric study of the copper-phenazopyridine monohydrochloride system in phosphate buffer medium

The electrochemical behavior of copper complexed with phenazopyridine monohydrochloride (2,6-diamino 3-phenylazo-pyridine monohydrochloride, pyridium) has been studied in 0.1 M phosphate buffer (pH 6.0). It was observed that Cu-II ions in the presence of pyridium are reduced at the mercury electrode in two distinct stages; this is a consequence of the interaction of pyridium with Cu-I ions. Tests showed that pyridium forms stable complexes with Cu-I and Cu-II ions. However, it was found that pyridium formed a 1:1 complex with Cu-I and a 1:2 complex with Cu-II ions.