The voltammetric determination of peroxynitrite at a mercury film electrode

This report describes the direct voltammetric detection of peroxynitrite (PN, ONOO^-), an important analyte in many physiological biochemical pathways, at a mercury film electrode (MFE) at alkaline pH. The voltammetric response of PN is observed as a cathodic inverted peak when the potential is swept in the oxidative direction at ca. -0.1 V vs. a Ag/AgCl/1 M KCl reference electrode. An mechanism is proposed to explain this behaviour involving the initial formation of a thin film of Hg(i) oxide on the electrode which is then oxidised by PN to form HgO in a chemical step. The HgO is then reduced back to Hg(0) at the electrode potential of interest resulting in a net cathodic current. The parameters affecting the voltammetry of PN at a MFE, including the concentration of PN (10^-5-10^-4 M), the effect of varying scan rate (5-100 mV s^-1) and pH are investigated and the kinetics of PN decay in alkaline solutions ranging from pH 9-13 are explored electrochemically.