This report describes the direct voltammetric detection of peroxynitrite (PN, ONOO-), an important analyte in many physiol. biochem. pathways, at a mercury film electrode (MFE) at alk. pH. The voltammetric response of PN is obsd. as a cathodic inverted peak when the potential is swept in the oxidative direction at ~-0.1 V vs. a Ag/AgCl/1 M KCl ref. electrode. An mechanism is proposed to explain this behavior involving the initial formation of a thin film of Hg(I) oxide on the electrode which is then oxidized by PN to form HgO in a chem. 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 concn. 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 alk. solns. ranging from pH 9-13 are explored electrochem. [on SciFinder(R)
An exact, sufficiently simple, explicit expression is obtained and a full contour of the stripping-voltammetry peak is calculated for a reversible process on a thin-film mercury electrode of finite thickness (linear boundedly semi-infinite diffusion is taken into account) in conditions of stripping voltammetry at a linearly altering potential. That these results were obtained at all, is due to use made of two extra boundary conditions (Nemov's and Nazarov's). The addends in the four forms of equations derived are the limiting expressions and "corrections" in the form of Nemov's or Nazarov's boundary conditions. It is shown that it is advisable to employ different forms of equations at large and small values of parameter H . The peak's height, full width at half-maximum, and potential are found to depend on H .
The full contour of a stripping-voltammetry peak for a reversible electrode process in conditions of boundedly semi-infinite and symmetrical diffusion on a thin-film mercury electrode at a linearly altering potential is calculated with an exact explicit equation allowing for the equilibrium-potential effect in a broad range of values of parameter H (which are defined by the film thickness, potential scan rate, and diffusion coefficient). The height, position of maximum, and full width at half-maximum of anodic peaks are evaluated as a function of parameter H and equilibrium potential. The latter is shown to exert substantial influence on the parameters and shape of anodic peaks.
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