Chapter 5 – Mineral Constituents
Résumé
Several mineral constituents can be detected by UV-visible spectrophotometry either directly (nitrate, nitrite, sulphide, hypochlorite and chromium) or indirectly after a photo-oxidation or a complexation step (ammonia, total nitrogen, iron, copper, mercury, etc.). Among the different mineral constituents, nitrate and phosphate ions are of primary importance regarding their impact on freshwater and coastal water quality (risk of eutrophication). The direct detection of nitrate ion in freshwater is one of the main application of UV spectrophotometry and high-frequency measurement is even possible with available commercial devices for temporally and spatially nitrate monitoring. For phosphate, the measurement is carried out with a colorimetric procedure, but simple analysers are also commercially available for high-frequency measurement. Other interesting applications for mineral constituents detection in water are also presented.