Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 686

12.6.5 Sulphite and cyanide
Goodwin et al. [72] determined traces of sulphite in clear or turbid potable waters by a
procedure based on gas dialysis/ion chromatography The detection limit was 2µg L −1 .
Ascorbic acid was required as an antioxidant to obtain good recoveries for potable and
well waters.
12.6.6 Arsenate, selenate and selenite
The procedure described in section 12.2.2 for the determination of arsenate, selenate and
selenite in non saline waters [22] has also been applied to potable waters.
12.6.7 Chlorite and chlorate
Chlorine dioxide (C1O 2 ) is a widely used disinfectant and bleaching agent that is
currently being used by many drinking water treatment utilities in the United States,
Canada and Europe for oxidation and disinfection. It is frequently applied as an initial
oxidant during treatment, followed by chlorination (gaseous C1 2 or HOCl) as a final
disinfectant. When used as an oxidant, chlorine dioxide reacts to form chlorite (C1O 2 − )
and chlorate (C1O 3 − ) which have been shown to cause haemolytic anaemia in laboratory
animals. Both C1O 2 − and C1O 3 − concentrations are currently under consideration for
regulation by EPA and because of possible adverse health effects will likely be regulated
with a maximum contaminant limit of <1.0mg L −1 for combined chlorine dioxide,
chlorite and chlorate.
Because regulations are imminent and the need exists to protect human health, accurate
methods for monitoring these compounds in drinking waters are needed.
In response to these needs Dietrich et al. [73] used flow injection analysis with
iodometric detection and ion chromatography with conductiometric detection in two
methods for the determination of chlorite and chlorate in chlorinated and chloroaminated
potable water.
The two methods were accurate and effective for reagent water. The ion
chromatographic method was accurate for measurement of chlorite and chlorate
concentrations in drinking water even in the presence of other oxidants including
chloramines. However, flow injection analysis was affected by chloramines and other
oxidants in drinking water, resulting in inaccurate determinations. While chlorite
concentrations were unstable in chlorinated drinking water, addition of sodium oxalate
increased the stability to up to 3 days and addition of ethylenediamine increased stability
up to 18 days. Chlorate concentrations were stable in drinking water for up to 18 days
with or without a preservative.
12.7 Waste waters
12.7.1 Bromide, chloride, fluoride, nitrate, nitrite, sulphate and phosphate