Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 86

2.4.10 Preconcentration
The preconcentration of arsenate is discussed in section 5.1.13.
2.5 Arsenite
2.5.1 Flow injection analysis
The application of this technique is discussed under multianion analysis in section
14.4.1.5.
2.5.2 Atomic absorption spectrometry
Arsenite (and arsenate and phosphate) have been determined in non saline waters by a
technique based on flotation spectrophotometry and extraction—indirect atomic
absorption spectrometry using malachite green as an ion-pair reagent [14].
2.5.3 Differential pulse polarography
Reed and Stolzberg [15] used differential pulse polarography for the direct determination
of arsenite in the presence of other arsenic species but there was significant interference
as a result of overlapping polarographic waves of lead, thallium and tin. Details are given
of procedure for removal of divalent lead and thallium by chromatography on a chelating
ion exchange resin. The presence of strong ligands could interfere with the removal of
lead but this interference could be prevented by the addition of divalent copper to
dissociate the lead complex. Since the interfering ions are removed from solution, large
amounts of lead and thallium could be tolerated.
2.5.4 Ion chromatography
Urasa and Ferede [16] used direct current plasma as an element-selective detector for the
simultaneous ion chromatographic determination of arsenic(III) and arsenic(V) in the
presence of other common anions. Matrix effects were eliminated, and a wide range of
element compositions can be used without experiencing detector limitations.
The application of this technique is also discussed under multianion analysis in section
12.2.2.
2.5.5 Ion exclusion chromatography
The application of this technique is discussed under multianion analysis in section
13.2.1.2.