Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 229

sulphonic acid

Miscellaneous Miscellaneous - - - [500]

8-amino phenyl N-(1-naphthyl) - - - [496]

Mercaptoacetic
acid

ethylene diamine - - - [501]

Source: Own files

coupling include reaction with 2,3-dimethyl-1-phenyl-pyrazolin-5-one [502], 2-
mercaptoethanol [503], mercaptoacetic acid [504], dihydroxy-4-imino-2-oxochroman
[505] and zirconyl ion [500,506,507].
Gabbay et al. [500] described a rapid spectrophotometric method in which nitrites react
with resorcinol in an acidic medium and the nitroso product forms a pale yellow chelate
with the zirconyl ion. The absorbance of the chelate is measured at 347nm. The method is
suitable for the determination of nitrite ion in a 1cm cell in the range from a few parts per
100 million to about 1mg L −1 .
Beer's law holds up to a concentration of 7mg L −1 of nitrite, as was demonstrated by
the calibration graph, which was a straight-line graph passing through the origin over this
range.
The effects of various potential interferences were investigated. Some of the
problematic interferents expected in the diazotisation methods such as sulphite, copper
(II), iron(II) or iodide, are tolerated in this procedure.
5,7-dihydroxy 4-imino-2-oxochroman has been used as a chromogenic reagent for the
spectrophotometric determination of nitrite in river waters [505].
The reagent was reacted with nitrate nitrogen in acidic medium, the product added to a
mixed solvent n -butyl alcohol and ethyl acetate, and absorbance measured at 361nm. The
amount of nitrite nitrogen was determined from the calibration curve. The relative
standard deviation was 0.3% for the determination of 0.1mg L −1 of nitrite. Beer's law
was obeyed over the range 0.005-0.280mg L −1 nitrite nitrogen.
Montes and Laserna [508] have described a spectrophotometric reaction rate method
for the determination of nitrite in water with pyridine-2 aldehyde-2-pyridylhydrazone. In
acidic medium the rate of the bromate oxidation of pyridine-2-aldehyde 2-
pyridylhydrazone is accelerated by nitrate. This kinetic principle was exploited for the
determination of sub-microgram quantities of nitrite in river samples. The reaction was
monitored spectrophotometrically at 372nm. The mean relative standard deviation for
nitrite determinations in polluted river water was 3.2%. Ammonium and nitrate ions did
not interfere but interferences from copper(II) and palladium(II) ions and electroactive
substances, were marked. The sensitivity of the kinetic method was less than for
established polarographic and chemiluminescence methods. However, this method was
more rapid than other spectrophotometric or polarographic procedures.
Ibraheem and Bashir [509] used para-aminoacetophenone as the diazotising reagent
and N -(1-naphthyl)ethylenediamine as the coupling reagent for a sensitive and simple
method for nitrite determination. The reddish-purple coloured azodye complex was
monitored by its absorption maximum at 550nm. Optimal conditions affecting the colour