High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose.
High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose.
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DOI：
10.1002/rcm.5302
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
E. Woodley;N. Loader;D. McCarroll;G. Young;I. Robertson;T. Heaton;M. Gagen;J. Warham
中科院分区：
文献类型：
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作者：
E. Woodley;N. Loader;D. McCarroll;G. Young;I. Robertson;T. Heaton;M. Gagen;J. Warham
纤维素的稳定同位素分析是生态和古环境研究的一个日益重要的方面。由于这些技术非常昂贵，任何能够同时测量纤维素中稳定的碳和氧同位素比率的方法开发都值得进一步探索。采用大量的树轮α-纤维素样品(3074个)，比较了高温(1400℃)裂解/气相色谱/同位素比质谱仪(δ(13)C)与燃烧气相色谱/红外光谱(GC/IRMS)所得的稳定碳同位素比值(C13C)。尽管这两个数据集具有很强的相关性，但热解结果显示出较小的方差，并且强烈偏向平均值。因此，上个世纪树木年轮纤维素的低碳同位素比率被高估了，这反映了大气二氧化碳的人为干扰。可能的解释是，一定比例的氧原子与反应室中的残余碳键合，形成一氧化碳。这里提出的“热解调整”是基于燃烧整个碳同位素比率范围内的热解结果的分层子样，并使用配对的结果来定义可用于调整所有热解测量的回归方程。在这项研究中，30个燃烧测量的子样本产生了调整后的年表，与通过燃烧每个样本产生的年表在统计上没有区别。这种方法允许使用高温热解同时测量碳和氧的稳定同位素，从而减少了单独测量它们所需的样本量和分析成本。
Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring α-cellulose samples are used to compare the stable carbon isotope ratios (δ(13)C) produced by high-temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately.