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100 C
6
H
5
COONa
Benzoate
14.80
4.62
Acetone
100 -
10.75
0.45
a
Results in the first column have an added nitrate concentration of 10mg L
−1
of N
b
Proprietary detergent
Source: Reproduced with permission from the Royal Society of Chemistry [491]
reduction method. The manual method (no dialysis) is prone to very significant positive
interference from the naturally occurring organic matter.
The interference effect of other substances is given in Table 7.15, and it can be seen
that the method is relatively free of interference effects for its intended uses. There was a
small positive bias from chromium(VI), acetone and humic acid, and a somewhat larger
bias from fulvic acid and the benzoate ion. However, the interference tests were carried
out at concentrations of these determinands considerably in excess of levels likely to be
encountered in potable waters.
7.18.4
Flow injection analysis
Al Wehaid and Townshend [53] describe flow injection spectrophotometric system
similar to that described by Van Staden
et al.
[54] for the determination of nitrate in
potable waters using titaneous chloride as reducing agent.
7.18.5
Polarography
The application of this technique is discussed under multianion analysis in section
14.10.2.1.
7.18.6
Ion chromatography
The application of this technique is discussed under multianion analysis in sections
7.28.2, 12.6.1, 12.6.2 and 12.6.3.
7.18.7
High performance liquid chromatography
Schroeder [55] determined nitrate in potable water using high performance liquid
chromatography with a reversed phase octadeyl C18 column using aqueous phosphoric
acid and dihydrogen phosphate as a mobile phase and ultraviolet detection. Detection
limits were 7µg L
−1
.
7.18.8
Ion exchange chromatography
Sherwood and Johnson [56] have described an ion exchange chromatographic
determination of nitrate and amperometric detection at a copperised cadmium electrode.
The chromatograms obtained in this procedure resolve nitrate from dissolved oxygen.
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