Determination of nitrate in natural waters by voltammetry at a stationary mercury drop electrode

The reliability of the method was established by good agreement of results with those obtained using spectrophotometry or liquid chromatography. The voltammetric method exploited the autocatalytic effect of the hydroxyl ions, formed at the surface of the electrode during the reduction of nitrate in the presence of an excess of trivalent cations such as cerium (III) or lanthanum (III). A repeatedly polarized stationary mercury drop electrode was used to enhance the autocatalytic effect of the reaction products on the electroreduction rate of nitrate. Humic substances present in natural waters had a favourable effect on nitrate determinations and levels of up to 20 mg phosphate per litre were tolerated by this method. The detection limit was 21 ug nitrate per litre.