Voltammetric determination of nitrate and nitrite ions using a rotating cadmium disk electrode

Abstract

Sir: Voltammetric procedures are described in the chemical literature for the quantitative determination of NOs™ and N02-in aqueous media based on their electrocatalyzed reductions at mercury electrodes in the presence of various diand trivalent cations (1-13). The mechanisms of these electrochemical reactions involve (i) the direct reduction of a complex formed between the cation and the nitrogen species or (ii) the enhancement of the voltammetric wave for the electroreduction of the cation when the reduced form of the cationic species is rapidly oxidized by NO3or N02~transported to the surface of the electrode by convective-diffusional processes. The uncatalyzed reductions of N03-and N02_ at mercury electrodes are sufficiently irreversible that the large cathodic current due to evolution of H2 obscures any cathodic wave for NO3or N02~.Direct electrochemical reductions of NO3-have been studied at a variety of other electrode materials, including Cu, Ti, Zn, Pb, Sn(Hg), Cu(Hg), Cr, and Pt (14-20). For none of these electrodes in dilute solutions of NO3can analytically useful cathodic waves be resolved from the wave due to evolution of H2. Well developed anodic waves for the oxidation of N02~t o NO3' at platinum electrodes are observed in the pH range 0.5-8 (21, 22). The process is strongly influenced by the extent of oxidation of the electrode surface (23). A quantitative method for determining N02~by oxidation at a platinum electrode in an acetic acid-acetate buffer was reported ( 23) in which controlledpotential coulometry was employed. We describe here cathodic current-potential curves recently obtained with a rotating cadmium disk electrode (RCDE) in weakly acidic solutions of NO3-and N02-. At low rotational velocities and bulk concentration, the cathodic currents are limited by convective-diffusional mass transport.

Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media

“…The transition metal cathodes exhibited volcano-shaped plots with respect to activity for NO À 3 reduction as a function of M-H and M-O bond energies with optimal activity corresponding to intermediate bond energies [2]. Studies of NO À 3 reduction also have been performed at Cu [3 ± 12], Cd [7,13,14], Pb [15,16] and Ag [4,17] electrodes, and at B-doped diamond electrodes [18 ± 20].…”

Green Approaches to Field Nitrate Analysis: An Electroanalytical Perspective

“…The current is monitored as a function of potential and offers a degree of selectivity in that the potential at which nitrate undergoes the reaction will be characteristic of the anion, electrode and electrolyte being used. A wide range of electrode substrates have been investigated and include silver [51], cadmium [52], platinum [53], gold [54] and, more recently, boron-doped diamond [55,56]. Various alloys and catalytic deposits have also been investigated, typically involving nickel [57], copper [58 -60], tin/palladium [61,62] and platinum/rhodium [63].…”

Electrochemical detection of nitrate in PM2.5 with a copper-modified carbon fiber micro-disk electrode

“…It is characterized by low sensitivity and irreproducibility and associated with surface passivation effects [29]. Therefore, a large number of strategies have been developed to modify electrode with some sensitive materials, such as copper [30,31], silver [32,33], cadmium [34,35], lead [36,37], palladium [38,39], polypyrrol materials [40], boron-doped diamond electrodes [41,42], and more recently, biocatalysts [43,44]. Among these materials, metallic copper is the most popular one because of its great advantages of low cost, good electrocatalysis and easy eletrodeposition [45][46][47].…”