Rotating ring-disk electrode method for the quantitative determination of nitrate ions in aqueous solutions in the submicromolar range

Abstract

be obtained experimentally. Such a potential is high enough to construct the plot up to the inflection point (0.264 V as determined by square wave voltammetry). The second half of the S-shaped plot was estimated as explained above. The slopes for the plateau region of the plot corresponding to pulse potentials of 0.408, 0.428, and 0.468 V were used to calculate an average electrochemical area using the Cottrell equation. To avoid interferences from adsorption, the potential pulse width was 250 ms. Extending the pulse duration up to 1 s did not significantly change the slope values, however. In calculation of the slope of Anson's plots, the BAS-100 ignores the first 20% of collected data and the slope measurement is then carried out in a time window where the effect of adsorption on the determination of the electrochemical area is of no consequence (10). Correlation coefficients were between 0.9970 and 0.9999. With the approach just outlined, untreated CP-01 surfaces showed electrochemical areas of 0.19 f 0.01 cm2 (0.21 cm2 geometrical area) compared with electrochemical areas of 0.43 f 0.01 cm2 after surfactant treatment. The removal of the film of pasting ingredient seems to increase the number of carbon centers available for electron exchange at the surface of the electrode. Increases in electrochemical area have been observed when polished electrodes based on Kel-F as inert ingredient were roughened and when the ratio of graphite to Kel-F was increased in the paste composition (11).Solutions of hexacyanoferrate(II1) in acidic media (HC1+ 1.0 M KC1) of pH 1.5-3.0 did not show much improvement in current by treatment with surfactant solutions 0.1% (w/v) for 10 min. Increasing the surfactant concentration to 1 % (w/v) and the treatment time to a t least 30 min, however, resulted again in an improved response of the treated surfaces.A rotating rlng-disk technique has been developed for the analytical determlnatlon of nitrate Ions In acid medla. I t Is based on the measurement of the ring currents associated with the oxldatlon of nitrite Ions generated by the reduction of nitrate Ions on a gold-dlsk electrode covered by a layer of underpotentlaliy deposited cadmlum. The ring currents were found to be proportlonal to the amount of nitrate In solution for concentrations In the mlllhnolar range down to 20-30 ppb. (1-19). The first is based on polarographic measurements conducted in the presence of certain polyvalent cations such as Zr02+, La3+, Yb3+, V02+, and Ce3+, which appear to promote the rates for nitrate reduction (1-15), whereas the second relies on cyclic voltammetry or dynamic polarization curves utilizing solid electrode materials capable of catalyzing the reduction of NO3- (16)(17)(18)(19). Davenport and Johnson (16,17), for instance, using a rotating cadmium-disk electrode obtained linear plots for the current as a function of the concentration of nitrate in the range of M. In related studies, Bodini and Sawyer (18) observed that the reduction of NO3was catalyzed by the simultaneous bulk deposition of c...

Electrochemical oxidation of nitrite on a rotating gold disk electrode: a second-order homogeneous disproportionation process

“…EXPERIMENTAL SECTION All electrochemical experiments were conducted in 0.1 M NaC104 aqueous solutions at pH 3, adjusted with ultrapure HC104 (J. T. Baker). The rotating gold-ring gold-disk electrode as well as the instruments used in the measurements were the same as those employed in earlier studies (1). Current-potential curves were recorded in the dynamic polarization mode at sweep rates of about 5-10 mV-s*1.…”

Determination of Nitrates in Water Samples by In‐Electrode Coulometric Titration in Copper Coated Porous Vitreous Carbon Electrode

“…The reversibility of the reduction can be enhanced by making use of some solid surface electrodes which are capable of catalysing the reduction of nitrate anions. Freshly deposited copper 14–19, cadmium 20, 21 and co‐deposited copper‐cadmium surfaces 22 were found the most effective catalysts for this purpose. Owing to possible contamination problems with toxic cadmium, the latter coating is less favoured.…”

An In Situ Copper Plated Boron‐Doped Diamond Microelectrode Array for the Sensitive Electrochemical Detection of Nitrate

“…A variety of techniques for the electrochemical reduction of nitrate over the years has been explored at metal electrode substrates such as cadmium [9,10], lead [11,12], silver [13], mercury [14,15], cadmium -copper alloy [16], copper [1, 3, 17 -19], an iridium deposited carbon fiber electrode [20], and boron-doped diamond [21 -23]. Though the majority of these studies focus on the associated fundamental electrolytic process.…”