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δ 34 S measurements on organic materials by continuous flow isotope ratio mass spectrometry
Author(s) -
Yun Misuk,
Mayer Bernhard,
Taylor Stephen W.
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1939
Subject(s) - chemistry , isotope ratio mass spectrometry , analytical chemistry (journal) , mass spectrometry , isotope , organic matter , sulfur , oxygen , isotopes of oxygen , decomposition , chromatography , nuclear chemistry , organic chemistry , physics , quantum mechanics
Sulfur (S) isotope ratios of thoroughly dried organic samples were measured by direct thermal decomposition in an elemental analyzer coupled to an isotope ratio mass spectrometer in continuous flow mode (EA‐CF‐IRMS). For organic samples of up to 13 mg weight and with total S contents of more than 10 μg, the reproducibility of the δ 34 S organic values was ±0.4‰ or better. However, the δ 34 S values of organic samples measured directly by online EA‐CF‐IRMS analysis were between 0.3 and 2.9‰ higher than those determined on BaSO 4 precipitates produced by Parr Bomb™ oxidation from the same sample material. Our results suggest that structural oxygen in organic samples influences the oxygen isotope ratios of the SO 2 produced from organic samples. Consequently, SO 2 generated from organic samples appears to have different 18 O/ 16 O ratios than SO 2 generated from BaSO 4 precipitates and inorganic reference materials, resulting in a deviation from the true δ 34 S values because of 32 S 16 O 18 O contributions to mass 66. It was shown that both the amount of structural oxygen in the organic sample, and the difference of the oxygen isotope ratios between organic samples and tank O 2 , influenced the magnitude of the observed deviation from the true δ 34 S value after direct EA‐CF‐IRMS analysis of organic samples. Suggestions are made to correct the difference between measured δ 34 S organic and true δ 34 S values in order to obtain not only reproducible, but also accurate S isotope ratios for organic materials by EA‐CF‐IRMS. Copyright © 2005 John Wiley & Sons, Ltd.