Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 234

calibration graph prepared from freshly prepared nitrite standards.
A calibration run was obtained using 0-30µg L −1 nitrite-nitrogen standards. The
method is claimed to be one of the most sensitive flow injection procedures available for
nitrite. The relative standard deviations of 10 injections each of solutions containing 10,
20 and 30µg L −1 nitrite-nitrogen were 1.3, 1.1 and 0.39% respectively. Samples with
higher concentrations of nitrite can be directly determined by decreasing the sample
volume injected and the recorder sensitivity. Linear calibration graphs were then obtained
up to 3mg L −1 nitrite-nitrogen (the maximum concentration tested). The sampling rate
was about 30 samples per h.
The effect of various ions on the determination of nitrite was also investigated. No
interference was caused by less than 50mg L − 1 Ca 2+ , Mg 2+ , K + , NH 4 + , HCO 3 − , SO4 2 −,
Cl − , SiO 3 2− , NO 3 − or H 2 PO 4 − in the determination of 30µg L −1 nitrite-nitrogen.
In Table 2.40 some results obtained upon applying this method to various non saline
water samples are shown.
Trojanek and Bruckenstein [526] have described a novel flow through penumato
amperometric detector the determination of nanogram and sub-nanogram amounts of
nitrite by flow injection analysis.
This gas porous electrode structure that detects volatile electroactive species in a
flowing liquid stream is described and evaluated for its utility in flow injection analysis.
The electrode is fabricated by depositing a porous gold layer on one side of a porous
Teflon membrane. The gold serves as the amperometric electrode which consumes
dissolved, volatile species that is transported from the flowing solution through the
membrane to the metallised face where it is electrolysed. Nitrite ion is determined by
reaction in the carrier stream to produce nitric oxide and iodine, and both are
electroxidised at the gold electrode. The detection limit is 30pg of nitrite ion. Dissolved,
non-volatile electroactive species do not interfere.
Zagatto et al. [527] have also discussed the application of flow injection analysis to the
determination of nitrite in non saline waters.
Vinas et al. [528] determined nitrite in non saline waters and waste-waters by a method
based on reverse flow injection analysis.
Workers at Tecator Ltd have devised flow injection analysis methods, based on the
sulphanilamide-N-(1-naphthyl) ethylenediamine reaction for the routine determination of
nitrite in various concentration ranges between 0.05-1, 10-100 and 30-100mg L −1 [529-
532].

2.63.5 Cathodic stripping voltammetry
Adsorptive cathodic stripping voltammetry was used by Van den Berg et al. [533] for
determining nanomolar levels of nitrite in freshwater and

Table 2.40 Recovery of nitrite added to non saline water samples

Amount of nitrite-N (µg L −1 )

Sample Recovery %