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| Titel |
First results from a novel methodological approach for δ¹⁸O analyses of sugars using GC-Py-IRMS |
| VerfasserIn |
Michael Zech, Matthias Saurer, Mario Tuthorn, Katja Rinne, Roland Werner, Dieter Juchelka, Rolf Siegwolf, Bruno Glaser |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074869
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| Zusammenfassung |
| Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ18O analyses is commercially available for more than 10 years, this method is hardly applied by isotope researchers so far. Using GC-Py-IRMS, Zech and Glaser (2009) and Zech et al. (2013; 2012) developed and applied a method, which allows determining δ18O of hemicellulose-derived sugar biomarkers extracted from soils and sediments. However, the used methylboronic acid (MBA) derivatization is suitable only for pentoses and deoxyhexoses, not for hexoses.
Here we present first GC-Py-IRMS results for TMS-(trimethylsilyl)-derivatives of plant sap-relevant sugars (glucose, fucose, sucrose, raffinose) and a polyalkohol (pinitol) produced using BSTFA (N,O-Bis(trimethylsilyl)trifluoroacetamide) as the derivatization reagent. Particularly, we focus on sucrose, which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and in tree-ring studies. Replicate analyses of sucrose standards with known δ18O values suggest that the δ18O measurements are not stable over several days. A calibration (including a drift correction) against an external sucrose standard is hence essential when measuring sample batches. Furthermore, we observed a large dependence of the δ18O values on the analyte amount (area), which needs to be considered by a respective correction procedure. Tests with 18O-enriched water do not provide any evidence for oxygen exchange reactions between water and sucrose, glucose and raffinose.
Finally we present the first application of compound-specific δ18O analyses from natural samples, namely from seven needle extracts (soluble carbohydrates) from a Siberian study area. Both the δ18O amplitude and values of sucrose are considerably higher (32.1‰ to 40.1‰) compared to the δ18O amplitude and values of bulk needle extract (24.6‰ to 27.2‰). We found positive correlation (although statistically not significant) for δ18O of sucrose (n = 7) and bulk δ18O (R = 0.62), δ13C of sucrose (R = 0.55) and maximum day temperature (R = 0.58) and negative correlation for δ18O of sucrose and cloudiness (R = -0.80). This highlights the great potential of compound-specific δ18O analyses of sucrose for (paleo-) plimate studies.
Zech, M., Glaser, B., 2009. Compound-specific d18O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and a first application. RCM 23, 3522-3532.
Zech, M., Tuthorn, M., Glaser, B., Amelung, W., Huwe, B., Zech, W., Zöller, L., Löffler, J., 2013. Natural abundance of 18O of sugar biomarkers in topsoils along a climate transect over the Central Scandinavian Mountains, Norway. JPNSS, in press.
Zech, M., Werner, R., Juchelka, D., Kalbitz, K., Buggle, B., Glaser, B., 2012. Absence of oxygen isotope fractionation/exchange of (hemi-) cellulose derived sugars during litter decomposition. Org Geochem 42, 1470-1475. |
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