Sample preservation prior to analysis - Determination of Anions in Natural and Treated Waters - page 782

total chromium is recommended as a method of checking on chromium reduction.
18.10 Selenate and selenite
Cheam and Agemian [20] studied the preservation and stability of inorganic selenium
compounds at µg L −1 levels in non saline water samples. They adopted the use of
sulphuric acid as the preserving medium as this was found not to interfere with the
hydride generation method they adopted for the determination of arsenite and arsenate.
They found that the use of polyethylene sample containers and pH adjustment to 1.5
(with 0.2 vol.% sulphuric acid) provided optimal conditions for the preservation of
samples for periods of up to 125 days. Storage at 4°C also preserves samples effectively
over the same time span.
References
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The Determination of Inorganic Anions in Water by Ion Chromatography. Method
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5 Water Research Centre, UK. Technical Report TR 214. Sample collection, preservation
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