Anions in seawater - Determination of Anions in Natural and Treated Waters - page 387

correlated with the temperature and with chlorophyll fluorescence.
Fig. 3.9 Detector response for a series of nitrate standards with concentrations
of 0, 10, 20 and 40µmol L −1
Source: Reproduced with permission from Springer Verlag [133]
3.20.6 Cathodic stripping voltammetry
Van den Berg [135] used this technique to determine nanomolar levels of nitrate in
seawater. Samples of seawater from the Menai Straits were filtered and nitrite present
reacted with sulphanilamide and naphthyl-amine at pH 2.5. The pH was then adjusted to
8.4 with borate buffer, the solution de-aerated and then subjected to adsorptive cathodic
stripping voltammetry. The concentration of dye was linearly related to the height of the
reduction peak in the range 0.3-200nM nitrate. The optimal concentrations of
sulphanilamide and naphthylamine were 2mM and 0.1mM respectively at pH 2.5. The