Yankuang ceshi (Jul 2019)
Determination of Oxygen Isotopic Composition in Barium Sulfate by Online Pyrolysis Method with Nickel-plated Carbon as Reductant
Abstract
BACKGROUND The oxygen isotopic composition of sulfate radical in mineral or water can be used to identify the source and transformation process. At present, the common method is to convert sulfate radical into barium sulfate and the oxygen isotopic composition determined offline or online. It is possible to shorten the working life of the furnace when δ18O of barium sulfate is measured online under 1420℃. The reaction temperature can be reduced by adding reductant carbon, but there is less discussion about the reaction temperature reported. OBJECTIVES To confirm the key technical parameters during determination of oxygen isotope composition in barium sulfate online. METHODS Nickel-plated carbon was added in a series of conditional experiments during determination of oxygen isotope composition of barium sulfate by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). RESULTS 1350℃ was chosen as the online pyrolysis temperature of barium sulfate by adding Ni-C. The sample size ratio between Ni-C and BaSO4 was set as 0.73-2.15. The sample weight of Ni-C and BaSO4 was 700±100μg, respectively. Under the above conditions, the precision of δ18O of BaSO4 measured by EA/HT-IRMS was ±0.12‰-±0.26‰, better than the reported results of ±0.20‰-±0.50‰. CONCLUSIONS On the premise of better precision, the online pyrolysis temperature of barium sulfate can be reduced to 1350℃ and the lifetime of the reactor can be improved by adding Ni-C.
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