Voltammetry of Electroinactive Species Using Quinone/Hydroquinone Redox: A Known Redox System Viewed in a New Perspective

Electrochemical behavior of p‐benzoquinone (Q), hydroquinone (H₂Q) and quinhydrone complex (QH) have been investigated in aqueous unbuffered solutions. The results revealed that in unbuffered solution the half wave potential of hydroquinone has a significant difference with quinone's half wave potential. It shown that, added acid in an unbuffered solution of Q, give rise to a new reduction peak at a more positive potential than original reduction peak of Q. The half‐peak potential of this new peak is dependent on acidity of added acid (pK_a) and its height is proportional to the acid concentration. Also, added base in an unbuffered solution of H₂Q, give rise to a new oxidation peak at a more negative potential than original oxidation peak of H₂Q. The half‐peak potential of this new peak is dependent on basicity of added base (pK_b) and its height is proportional to the base concentration. This paper shows new perspectives for a known system in aqueous unbuffered solutions, by means of voltammetric responses that can be exploited for the electrochemical investigation of non electroactive species such as HPO , HCO or CH₃COOH.