Comparison of 18O Measurements in Nitrate by Different Combustion Techniques
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- 作者：Kinga Ré ; vé ; sz and John-Karl Bö ; hlke
- 刊名：Analytical Chemistry
- 出版年：2002
- 出版时间：October 15, 2002
- 年：2002
- 卷：74
- 期：20
- 页码：5410 - 5413
- 全文大小：63K
- 年卷期：v.74,no.20(October 15, 2002)
- ISSN：1520-6882
文摘
Three different KNOB>3 salts with 
18O values ranging fromabout -31 to +54” relative to VSMOW were used tocompare three off-line, sealed glass tube combustionmethods (widely used for isotope studies) with a morerecently developed on-line carbon combustion technique.All methods yielded roughly similar isotope ratios forKNO3 samples with 18O values in the midpoint of the18O scale near that of the nitrate reference material IAEA-NO-3 (around +21 to +25”). This reference material hasbeen used previously for one-point interlaboratory andintertechnique calibrations. However, the isotope ratioscale factors by all of the off-line combustion techniquesare compressed such that they are between 0.3 and 0.7times that of the on-line combustion technique. Thecontraction of the 18O scale in the off-line preparationsapparently is caused by O isotope exchange between thesample and the glass combustion tubes. These resultsreinforce the need for nitrate reference materials with18O values far from that of atmospheric O2, to improveinterlaboratory comparability.
18O values ranging fromabout -31 to +54” relative to VSMOW were used tocompare three off-line, sealed glass tube combustionmethods (widely used for isotope studies) with a morerecently developed on-line carbon combustion technique.All methods yielded roughly similar isotope ratios forKNO3 samples with 18O values in the midpoint of the18O scale near that of the nitrate reference material IAEA-NO-3 (around +21 to +25”). This reference material hasbeen used previously for one-point interlaboratory andintertechnique calibrations. However, the isotope ratioscale factors by all of the off-line combustion techniquesare compressed such that they are between 0.3 and 0.7times that of the on-line combustion technique. Thecontraction of the 18O scale in the off-line preparationsapparently is caused by O isotope exchange between thesample and the glass combustion tubes. These resultsreinforce the need for nitrate reference materials with18O values far from that of atmospheric O2, to improveinterlaboratory comparability.