Introduction - Determination of Anions in Natural and Treated Waters - page 79

11.2.4.1(b)

Sulphate 11.1.4.2(h)

11.2.5.1(b)

11.1.4

Sulphite 11.2.6.1(b)

Source: Own files

water sample that is applicable to the type of sample of interest. Thus, if a method is not
available for determining a particular anion in say non saline water, he or she may find
one is listed under potable water. Obviously this approach will not always be applicable,
thus a method listed under trade effluents is not likely to be applicable to the ultra low-
level analysis of potable, natural or sea waters.
The various methods of determining anions are discussed below in order of the number
of applications found for each technique.

1.2.1 Chromatographic techniques

By far the most extensively used techniques are chromatographic techniques such as ion
chromatography, high performance liquid chrom-atography, gas chromatography and
other chromatographic techniques.
Ion chromatographic and high performance liquid chromatographic techniques have
been obvious advantages of good sensitivity, specificity, multicomponent analysis and
automation of the analytical procedure.
In all 85 anions have been determined by ion chromatography of which 31 are
inorganic anions and 54 are organic anions. The relatively new technique of electrostatic
ion chromatography has, to date, only found application in the determination of bromide
application in iodide and nitrite.
Some 40 anions have been determined by high performance liquid chromatography; 25
inorganic and 15 organic anions. Ion exclusion chromatography has been applied to some
19 anions; 11 inorganic and eight organic.
Similarly, micelle chromatography has been applied to the determination of 10 anions.
Ion pairing chromatography has very few applications to date (two inorganic anions). Ion
exchange chromat-ography has been applied to the determination of six inorganic anions.
Gas chromatographic methods are limited by the need for appropriate chemistry to
convert anions to a volatile form. Methods of achieving this have been described in the
cases of arsenate, bromide, chlorite, cyanide, fluoride, iodide, nitrate, nitrite, phosphate,
sulphate, selenate, selenite, sulphide and thiocyanide.

1.2.2 Titration techniques

Titration procedures have been developed for 19 anions. These generally lack in
sensitivity and specificity. They should be used only when analysis is required at the mg
L −1 level and when the possible interference effects by other anions or cations present in
the sample is fully understood.