Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry |
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Authors: | HN Elsheimer TL Fries |
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Institution: | U.S. Geological Survey, Menlo Park, CA 94025 U.S.A. |
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Abstract: | A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 μg l?1 of tin in the MIBK solution or 0.2–0.3 μg g?1 in the rock. The concentration range is linear between 2.5 and 500 μg l?1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 μg l?1 level and < 7% at the 10–30 μg l?1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 μg g?1 or less. |
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Keywords: | Tin Rocks |
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