Spectral and Electrochemical Studies of Phenazopyridine

The spectral and voltammetric behavior of phenazopyridine (1) in aqueous buffers of varied pH is presented. Spectrophotometry, cyclic voltammetry, differential pulse polarography and coulometry were utilized to study its proton and electron transfer characteristics. Relevant thermodynamic and electrochemical data such as pK a, charge transfer co-efficient ( na ), forward rate constant (k 0f,h ), etc., have been evaluated. An excellent electroanalytical method of assaying of 1 has been developed in differential pulse polarography at pH = 8. Molecular modeling on various acid-base conjugates of 1 and their several conformers has been carried out to arrive at the thermodynamic and conformational issues to correlate the spectral and electrochemical observations.