Nitrate, voltammetric determination

The voltammetric determination of nitrate following a preconcentration step using Permion 1025 was developed by Cox, Lundquist and Washinger (33). Nitrate is exchanged from the sample solution through the membrane into a small volume cell contain ing 0.1 M potassium chloride and 0.01 M lanthanum chloride. The method eliminates cationic interferences with the voltammetry but does not successfully deal with anionic interferences such as a sulfate or nitrite. 

Neuhold C, Kalcher K, Diewald W, Cai X, Raber G (1994) Voltammetric determination of nitrate with a modified carbon paste electrode. Electroanalysis 6 227-236... 

The combination of the enrichment and enhancement effects in CAdSV has been successfully used for reactions involving either a single or a two-electron reduction. As indicated in Table 3, the inclusion of oxidants, such as nitrite, nitrate, peroxide, bromate, chlorite, chlorate, and hydrogen ions, in solutions have been shown to result in (1) considerable amplification of the voltammetric responses obtained with AdSV, (2) a reduction in detection limits, and (3) improved selectivity. This catalytic current generation has been successfully used for the AdSV determination of inorganic substances, such as Co, Cr,... 

Electrochemically inactive organic compounds can be converted into an electrochemically active state by nitration, nitrosation, oxidation, hydrolysis, or some other preliminary chemical reaction, and can then be determined polarographically or voltammetrically. Examples of this are polarographic determinations of alkylbenzenesulfonates in natural water samples after extraction and nitration of the aromatic ring [77] and determinations of beta-receptor blocking agents in tablets after conversion to the corresponding V-nitroso derivatives [78]. 

The voltammetric method to determine chromium is sensitive in seawater and even more sensitive (10x more) in freshwater. It is an interesting method because of some unusual changes in the oxidation state of chromium during the analysis. The sensitivity is high due to a catalytic effect caused by the reduction product of chromium(///) (chromium(//)) on the electrochemical reduction of nitrate. Analysis is therefore carried out in the presence of a high concentration of nitrate which greatly enhances the sensitivity. 

Campos, I., Masot, R., Alcaniz, M. et al. (2010) Accurate concentration determination of anions nitrate, nitrite and chloride in minced meat using a voltammetric electronic tongue. Sens. Actuators, B, 149,71-78. 

Selected voltammetric methods for the determination of nitrated explosives are summarized in Table 12.1, showing broad scope of explosives, techniques, electrodes, and matrices investigated for those purposes. 

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