Determination of indium in natural waters by flow injection inductively coupled plasma mass spectrometry |
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Authors: | Dia Sotto Alibo Hiroshi Amakawa Yoshiyuki Nozaki |
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Institution: | (1) Marine Inorganic Chemistry Division, The Ocean Research Institute, University of Tokyo, Nakano-ku, 164 Tokyo, Japan |
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Abstract: | Two methods have been developed to measure indium (In) in natural waters by flow injection inductively coupled plasma mass
spectrometry (ICPMS). One is the isotope dilution technique using an113In enriched spike and the other utilizes natural yttrium present in the sample as an internal standard. In the former, optimization
of the113In spike to minimize error is often difficult for samples in which In concentrations are variable, whereas in the latter method,
a separate determination of Y in the sample is necessary and hence more sample is required. Using about 1 liter of a water
sample, 200 fold preconcentration of In was performed by solvent extraction and back extraction technique and then introduced
into the ICPMS to measure the113In/115In or115In/89Y ratios. The detection limits were 0.01–0.02 pmol kg−1 for both methods.
Application of the methods to seawater samples yielded the concentrations of 0.06–0.15 pmol kg−1 for the Pacific and 0.6–1.5 pmol kg−1 for the Atlantic. The large inter-oceanic variation of In best resembles that of Al amongst the 3B group of elements in the
periodic table. River and estuarine samples gave a more variable range of concentrations of 0.01–15 pmol kg−1. Most of the In supplied by rivers is removed by scavenging in the estuarine mixing zone, suggesting that the fluvial input
of In to the ocean is small. |
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Keywords: | Indium dissolved indium ICPMS isotope dilution method oceanic distribution |
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