Sulfur trace determination in petroleum products by isotope dilution ICP-MS using direct injection by thermal vaporization (TV-ICP-IDMS) |
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Authors: | Jens Heilmann Klaus G Heumann |
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Institution: | (1) Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg University, Duesbergweg 10–14, 55099 Mainz, Germany |
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Abstract: | An accurate, sensitive, and fast method for direct determination of total sulfur in petroleum products after thermal vaporization
of an isotope-diluted sample was developed by using ICP-MS. 34S-labelled dibenzothiophene spike was used for the isotope dilution step. The isotope-diluted sample was injected into a thermal
vaporizer which was directly connected by a heated transfer line to the plasma torch. Sample transport was achieved by using
a helium gas flow, and the isotope ratio 34S/32S was determined within seconds after injection. No other sample preparation other than the simple and fast isotope dilution
step, which enables accurate and sensitive determination of sulfur at high sample throughputs, is necessary. Thus, this technique
fits all needs for routine analyses. Validation of the TV-ICP-IDMS method was carried out by analyzing the certified gas oil
reference materials BCR672 and BCR107. Comparison of results for noncertified low- and high-boiling samples, obtained from
an ICP-IDMS microwave-assisted digestion method, also resulted in very good agreement. The low detection limit of 40 ng/g
and the large dynamic range of TV-ICP-IDMS fulfill all necessities to allow analysis of sulfur in different petroleum products,
e.g., even at the low concentration level of ‘sulfur-free’ gasoline. |
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Keywords: | Sulfur trace determination Isotope dilution ICP-MS Petroleum products Thermal vaporization Routine analysis |
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