Nitrate/nitrite in seawater (cadmium reduction method)

Nitrate/Nitrite in seawater (Cadmium reduction method)

(Lachat QuickChem method #31-107-04-1-C; http://www.lachatinstruments.com/)

Principle

Nitrate is quantitatively reduced to nitrite by passage of the sample through a copperized cadmium column. The nitrite (reduced nitrate plus original nitrite) is then determined by diazotizing with sulfanilamide followed by coupling with N-(1-naphthyl) ethylenediamine dihydrochloride. The resulting solution has a magenta color, which is detectable at 520 nm.

Procedure

Nitrite/nitrate will be determined on autoanalyser/flow injection analyser following the standard colorimetric methods (Grasshoff et al. 1983). Samples containing high concentrations of iron, copper or other metals may give low results. EDTA is added to the buffer to reduce this interference.

References.

Grasshoff, K., Ehrhardt, K. and kremling, K., (1983). Methods of seawater analysis. Verlag Chemie, Weinheim, New York.