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DOI 10.1002/rcm.3958
Title (Primary) Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques
Author Brand, W.A.; Coplen, T.B.; Aerts-Bijma, A.; Böhlke, J.K.; Gehre, M.; Geilmann, H.; Gröning, M.; Jansen, H.G.; Meijer, H.A.J.; Mroczkowski, S.J.; Qi, H.; Soergel, K.; Stuart-Williams, H.; Weise, S.M.; Werner, R.A.
Source Titel Rapid Communications in Mass Spectrometry
Year 2009
Volume 23
Issue 7
Page From 999
Page To 1019
Language englisch
Abstract Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of hightemperature conversion techniques (HTC)a in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125%, an artificially enriched reference water (d18O of R78.91%) and two barium sulfates (one depleted and one enriched in 18O) were prepared and calibrated relative to VSMOW2b and SLAP reference waters. These materials were used to calibrate the other isotopic reference materials in this study, which yielded:Reference material d18O and estimated combined uncertaintyIAEA-602 benzoic acid þ71.280.36%USGS35 sodium nitrate þ56.810.31%IAEA-NO-3 potassium nitrate þ25.320.29%IAEA-601 benzoic acid þ23.140.19%IAEA-SO-5 barium sulfate þ12.130.33%NBS 127 barium sulfate þ8.590.26%VSMOW2 water 0%IAEA-600 caffeine 3.480.53%IAEA-SO-6 barium sulfate 11.350.31%USGS34 potassium nitrate 27.780.37%SLAP water 55.5%According to IUPAC rules delta is defined as dB,RŒrB/rR - 1 (with rB being the isotope amount ratio in sample B and rR in reference R, without the extraneous factor 1000). In this paper we express the corresponding delta values either as 103 dB,R or we use the % sign behind the number, depending on space availability and readability.The seemingly large estimated combined uncertainties arise from differences in instrumentation and methodology and difficulty in accounting for all measurement bias. They are composed of the 3-fold standard errors directly calculated from the measurements and provision for systematic errors discussed in this paper. A primary conclusion of this study is that nitrate samples analyzed for d18O should be analyzed with internationally distributed isotopic nitrates, and likewise for sulfates and organics. Authors reporting relative differences of oxygen-isotope ratios (d18O) of nitrates, sulfates, or organic material should explicitly state in their reports the d18O values of two or more internationally distributed nitrates (USGS34, IAEA-NO-3, and USGS35), sulfates (IAEA-SO-5, IAEA-SO-6, and NBS 127), or organic material (IAEA-601 benzoic acid, IAEA-602 benzoic acid, and IAEA-600 caffeine), as appropriate to the material being analyzed, had these reference materials been analyzed with unknowns. This procedure ensures that readers will be able to normalize the d18O values at a later time should it become necessary.The high-temperature reduction technique for analyzing d18O and d2H is not as widely applicable as the well-established combustion technique for carbon and nitrogen stable isotope determination. To obtain the most reliable stable isotope data, materials should be treated in an identical fashion; within the same sequence of analyses, samples should be compared with working reference materials that are as similar in nature and in isotopic composition as feasible.
Persistent UFZ Identifier
Brand, W.A., Coplen, T.B., Aerts-Bijma, A., Böhlke, J.K., Gehre, M., Geilmann, H., Gröning, M., Jansen, H.G., Meijer, H.A.J., Mroczkowski, S.J., Qi, H., Soergel, K., Stuart-Williams, H., Weise, S.M., Werner, R.A. (2009):
Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques
Rapid Commun. Mass Spectrom. 23 (7), 999 - 1019 10.1002/rcm.3958