An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography–mass spectrometry

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Schouten, Stefan
Hopmans, Ellen C.
van der Meer, Jaap
Mets, Anchelique
Bard, Edouard
Bianchi, Thomas S.
Diefendorf, Aaron
Escala, Marina
Freeman, Katharine H.
Furukawa, Yoshihiro
Huguet, Carme
Ingalls, Anitra
Menot, Guillemette
Nederbragt, Alexandra J.
Oba, Masahiro
Pearson, Ann
Pearson, Emma J.
Rosell-Mele, Antoni
Schaeffer, Philippe
Shah, Sunita R.
Shanahan, Timothy M.
Smith, Richard W.
Smittenberg, Rienk
Talbot, Helen M.
Uchida, Masao
Van Mooy, Benjamin A. S.
Yamamoto, Masanobu
Zhang, Zhaohui
Sinninghe Damste, Jaap S.
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Recently, two new proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were proposed, i.e., the TEX86 proxy for sea surface temperature reconstructions and the BIT index for reconstructing soil organic matter input to the ocean. In this study, fifteen laboratories participated in a round robin study of two sediment extracts with a range of TEX86 and BIT values to test the analytical reproducibility and repeatability in analyzing these proxies. For TEX86 the repeatability, indicating intra-laboratory variation, was 0.028 and 0.017 for the two sediment extracts or ±1–2°C when translated to temperature. The reproducibility, indicating among-laboratory variation, of TEX86 measurements was substantially higher, i.e., 0.050 and 0.067 or ±3–4°C when translated to temperature. The latter values are higher than those obtained in round robin studies of Mg/Ca and U37 k′ paleothermometers, suggesting the need to primarily improve compatibility between labs. The repeatability of BIT measurements for the sediment with substantial amounts of soil organic matter input was relatively small, 0.029, but reproducibility was large, 0.410. This large variance could not be attributed to specific equipment used or a particular data treatment. We suggest that this may be caused by the large difference in the molecular weight in the GDGTs used in the BIT index, i.e., crenarchaeol versus the branched GDGTs. Potentially, this difference gives rise to variable responses in the different mass spectrometers used. Calibration using authentic standards is needed to establish compatibility between labs performing BIT measurements.
Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 10 (2009): Q03012, doi:10.1029/2008GC002221.
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Geochemistry Geophysics Geosystems 10 (2009): Q03012
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