Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 248

Alawi [582] has discussed an indirect method for the determination of nitrite and
nitrate in surface, ground and rain water by reaction with excess phenol (nitrite ions first
being oxidised to nitrate) and extraction of the o-nitrophenol produced, followed by
separation on a reversed phase high performance liquid chromatography column with
amperometric detection in the reduction mode. Recoveries were 82% for nitrate and 77%
for nitrite in the concentration range 10-1000µg L −1 . The method is claimed to be free of
interferences from other ions.
U sing a radial compression C 18 column and a mobile phase of aqueous
tetramethylammonium phosphate Kok et al. [583] analysed mixtures of nitrate and nitrite
at the 0.1mg L −1 level (3α) and compared the results obtained with those found by
ultraviolet spectroscopic screening methods.
Marengo et al. [584] have discussed experimental design and partial least squares for
the optimisation of reversed phase ion interaction liquid chromatographic separation of
nitrite, nitrate and phenylenediamine isomers. Levels down to 0.5mg L −1 of these

substances were determined.
The application of this technique is also discussed under multianion analysis in
sections 13.1.1.3, 13.1.1.4 and 13.1.1.5.

2.64.16 Ion exchange chromatography
Davenport and Johnson [585] used ion exchange chromatography on Amberlite IRA-900
strongly basic resin to determine nitrate and nitrite in water. 0.01M perchloric acid was
used as eluent and an electrochemical cadmium electrode detector was used.
Sherwood and Johnson [477] 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.

2.64.17 Micelle exclusion chromatography
Okada [375] has used micelle exclusion chromatography to determine nitrite and nitrate
in the presence of other anions (bromide, iodide and iodate) in water. The method is
based on partition of ions to a cationic micelle phase and shows different selectivity from
ion exchange chromatography.
The application of this technique is also discussed under multianion analysis in section
13.5.1.2.

2.64.18 Miscellaneous
Marti and Hale [560] compared automated segmented flow and discrete analysers for the
determination of nitrite, nitrate, ammonia and phosphate. The discrete analyser provided
a 50% increase in the rate of analysis compared with segmented-flow analysis. The
accuracy and precision were comparable. While both methods are in agreement, the rate
of analysis (60 samples per h) was faster by discrete analysis than segmented-flow
analysis (40 samples per h).
Nagashima et al. [586] determined nitrate and nitrite by using second derivative