Anions in trade effluents - Determination of Anions in Natural and Treated Waters - page 592

10.10 Nitrate

10.10.1 Spectrophotometric method
Dodin et al. [35] observed when a solution of nitrate at pH 2.0 is irradiated with
ultraviolet light nitrate will oxidise methyl orange. They used this as the basis of a
Spectrophotometric method for determining nitrate in industrial effluents.

10.10.2 Ion chromatography
The application of this technique is discussed under multianion analysis in sections
10.22.1 and 12.8.1.

10.11 Nitrite

10.11.1 Spectrophotometric method

Maly and Kosikova [36] have described two Spectrophotometric methods for the
determination of nitrites in industrial effluents. These workers compared their methods
with the standard method using sulphanilic acid and N-(1-naphthyl)ethylenediamine and
a new modification of the process with sulphanilic acid and 1-naphthol. The advantage of
the latter is the possibility of diluting coloured solutions where, owing to high nitrite
concentrations, the absorbance exceeds the range of the calibration curve. Urea and
glycine (up to 100mg L −1 ) do not interfere with these methods. Iron at levels about 5mg
L −1 can be eliminated by clarifying the sample with an aluminium salt.

10.11.2 Amperometry

Oxidation flow injection amperometry using an electrochemically pretreated glassy
carbon electrode has been used to determine nitrite in water [37].

Table 10.2 Interference effects in the determination of phosphate by the molybdenum
blue method

Arsenate serious interference

will tolerate 10mg L −1 silicon

Silicon

1mg L −1 interferes

Chromium

Oxidising agents may interfere

1mg L −1 tolerated

Nitrite

Nitrate 20g L−1 tolerated