A novel methodological approach for delta O-18 analysis of sugars using gas chromatography-pyrolysis-isotope ratio mass spectrometry

作者：Zech Michael^*; Saurer Matthias; Tuthorn Mario; Rinne Katja; Werner Roland A; Siegwolf Rolf; Glaser Bruno; Juchelka Dieter

来源：Isotopes in Environmental and Health Studies, 2013, 49(4): 492-502.

DOI：10.1080/10256016.2013.824875

• evaporative isotope enrichment
• isotope ecology
• isotope measurements
• methods and equipment
• oxygen-18
• paleoclimatology
• plant physiology
• sugars
• sucrose

Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific O-18 analysis has been commercially available for more than a decade, this method has been hardly applied so far. Here we present the first GC-Py-IRMS O-18 results for trimethylsilyl-derivatives of plant sap-relevant sugars and a polyalcohol (glucose, fructose, sucrose, raffinose and pinitol). Particularly, we focus on sucrose, which is assimilated in leaves and which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and paleoclimate studies. Replication measurements of sucrose standards and concentration series indicate that the GC-Py-IRMS O-18 measurements are not stable over time and that they are amount (area) dependent. We, therefore, suggest running sample batch replication measurements in alternation with standard concentration series of reference material. This allows for carrying out (i) a drift correction, (ii) a calibration against reference material and (iii) an amount (area) correction. Tests with O-18-enriched water do not provide any evidence for oxygen isotope exchange reactions affecting sucrose and raffinose. We present the first application of GC-Py-IRMS O-18 analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained O-18(sucrose/ Vienna Standard Mean Ocean Water (VSMOW)) values are more positive and vary in a wider range (32.1-40.1 parts per thousand) than the O-18(bulk/ VSMOW) values (24.6-27.2 parts per thousand). Furthermore, they are shown to depend on the climate parameters maximum day temperature, relative air humidity and cloud cover. These findings suggest that O-18(sucrose) of the investigated needles very sensitively reflects the climatically controlled evaporative O-18 enrichment of leaf water and thus highlights the great potential of GC-Py-IRMS O-18(sucrose) analysis for plant physiology and paleoclimate studies.

• 出版日期2013-12-1