Ion Chromatographic Determination of Fluorine and Chlorine in Silicate Rocks Following Alkaline Fusion |
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Authors: | Kenji Shimizu Takaaki Itai Minoru Kusakabe |
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Institution: | Institute for Study of the Earth's Interior, Okayama University, Misasa, Tottori 682-0193, Japan |
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Abstract: | A simple and accurate method to determine fluorine and chlorine contents in small amounts (~ 30 mg) in rock has been developed using ion chromatography after extraction by alkaline fusion. Powdered sample was mixed with sodium carbonate and zinc oxide at a mass ratio of 1:3:1, and was fused in an electric furnace at 900 °C for 30-40 minutes. An aqueous solution obtained by dissolving the fused silicate rock was diluted to the appropriate concentration of sodium carbonate (< ~ 24 mmol l-1) to minimise the tailing effect on F- during ion chromatography caused by the large amount of carbonate species originating from the flux. Fluorine and chlorine contents were then determined by a standard additions method. Based on the relative standard deviation of the backgrounds, detection limits of both fluorine and chlorine were ~ 4 μg g-1, when 30 mg test portions were fused and diluted by a factor of 1200. We also report new fluorine and chlorine contents in nine GSJ (Geological Survey of Japan) reference materials, including peridotite (JP-1), granite (JG-1a), basalts (JB-1b, 2 and 3), andesites (JA-1 and 2) and rhyolites (JR-1 and 2). Fluorine and chlorine contents in the reference materials in this study were consistent with previously reported values. Reproducibilities were < 10 % for samples with F and Cl concentrations of > 20 μg g-1 and < 20 % with F and Cl < 20 μg g-1. |
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Keywords: | fluorine chlorine ion chromatography alkaline fusion GSJ reference materials |
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