A rapid colorimetric paper-based screening method for measuring mercury in marine systems

Cavoura, Olga and Keenan, Helen and Davidson, Christine (2011) A rapid colorimetric paper-based screening method for measuring mercury in marine systems. In: 10th International Conference on Mercury as a Global Pollutant, 2011-07-24 - 2011-07-29. (Unpublished)

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Abstract

There is considerable current interest in the development of simple, cheap analytical approaches for measuring potentially toxic metals and organometallics in the environment, especially methods that are field-deployable and that can be used by individuals with no scientific training. Amongst the simplest of these are paper-based sensors [1]. These test strips are analogous to litmus paper in that they are impregnated with reagent(s) that change colour on exposure to a specific pollutant, the intensity of which can be estimated ‘by-eye’ or read out by an electronic device, and relates to the pollutant concentration present. Key analytical challenges in the development of such sensors include ensuring that they are selective, sensitive and stable. Such a method has recently been reported for mercury involving reduction of inorganic mercury to elemental mercury and trapping on detecting papers with a copper iodide coating [2]. A preliminary sample digestion procedure is added for the determination of analyte in solid samples. The approach – which has been implemented previously in soil and fresh water sediment – is here evaluated for its applicability in the marine environment. Sensitivity and reproducibility were tested in distilled water, artificial seawater of different salinities, and in real environmental samples. Distinctions could be observed between the responses of solutions whose concentrations differed by at least 20 mg L-1 over a range from 15 – 100 mg L-1, and whose concentrations differed by at least 50 mg L-1 in the range from 100 – 250 mg L-1. The effective detection limit was ~ 15 mg L-1. Salinity ranging from 0-40 psu did not appear to affect significantly the response of the method. The procedure was applied as a screening analysis to provide a preliminary estimate of levels of mercury in contaminated marine sediment obtained from the Gulf of Elefsina, Greece. Sediment samples containing > 100 ng/g mercury were successfully identified, as confirmed by cold vapour atomic absorption spectroscopy.

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