Field based speciation of arsenic in UK and Argentinean water samples |
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Authors: | M J Watts J O’Reilly A L Marcilla R A Shaw N I Ward |
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Institution: | (1) British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK;(2) Chemical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK |
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Abstract: | A field method is reported for the speciation of arsenic in water samples that is simple, rapid, safe to use beyond laboratory
environments, and cost effective. The method utilises solid-phase extraction cartridges (SPE) in series for selective retention
of arsenic species, followed by elution and measurement of eluted fractions by inductively coupled plasma mass spectrometry
(ICP-MS) for “total” arsenic. The method is suitable for on-site separation and preservation of arsenic species from water.
Mean percentage accuracies (n = 25) for synthetic solutions of arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MA), and dimethylarsinic acid (DMA) containing 10 μg l−1 As, were 98, 101, 94, and 105%, respectively. Data are presented to demonstrate the effect of pH and competing anions on
the retention of the arsenic species. The cartridges were tested in the UK and Argentina at sites where arsenic was known
to be present in surface and groundwaters, respectively, at elevated concentrations and under challenging matrix conditions.
In Argentinean groundwater, 4–20% of speciated arsenic was present as MA and 20–73% as AsIII. In UK surface waters, speciated arsenic was measured as 7–49% MA and 12–42% DMA. Comparative data from the field method
using SPE cartridges and the laboratory method using liquid chromatography coupled to ICP-MS for all water samples provided
a correlation of greater than 0.999 for AsIII and DMA, 0.991 for MA, and 0.982 for AsV (P < 0.01). |
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