On the necessity of organic solvent extraction for carbon isotopic analysis of α-cellulose: implications for environmental reconstructions
On the necessity of organic solvent extraction for carbon isotopic analysis of α-cellulose: implications for environmental reconstructions
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DOI：
10.1080/03067310903410949
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发表时间：
2010-04
影响因子：
2.6
通讯作者：
F. Tao;Y. Liu;Ning An
中科院分区：
文献类型：
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作者：
F. Tao;Y. Liu;Ning An
α-纤维素是环境重建中广泛应用的同位素比值分析的目标物质。其制备包括有机溶剂萃取、脱木素和碱水解三个基本步骤。最近的研究表明省略了第一步。利用32个连续的树木年轮和30个亚化石泥炭样品，对有机溶剂抽提前后的α-纤维素碳同位素比值进行了详细的比较。将这些样品暴露于三种不同的化学处理：有机溶剂提取作为第一步（CellOE），无有机溶剂提取（CellNOE），以及有机溶剂提取作为最后一步（CellNOE/OE）。第三种处理用于测试有机抽提物是否可以完全除去，或者它们在有机溶剂中的溶解度是否已经通过脱木质素和碱水解而改变。在树木年轮和泥炭中，δ 13 CC ell NOE与δ 13 CC ell OE始终存在显著差异，但变化趋势并不一致。在树木年轮中，δ 13 CC ell NOE总是比δ 13 CC ell OE负-0.31-0.01 ‰。相反，泥炭的δ 13 CC ell NOE可能比δ 13 CC ell OE更负或更正，负3.08 <$0.27 ‰。第三次化学处理导致不同的模式。对于树木年轮，δ 13 CC ell NOE/OE仍然比δ 13 CC ell OE负-0.36-0.08 ‰。泥炭的δ 13 CC ell NOE/OE与δ 13 CC ell OE的差值较之δ 13 CC ell NOE与δ 13 CC ell OE的差值在-0.58 ~0.61 ‰之间，反映了泥炭在脱木素和碱解过程中复杂的化学演化行为和脂类的不完全去除。的平均值，长期趋势和跷跷板模式的树木年轮或泥炭CellNOE系列显着不同的CellOE系列，这表明有机溶剂提取的省略将导致过去的环境条件有偏见的推断。
α-cellulose is widely used as a target substance for isotope ratio analysis in environmental reconstructions. Its preparation includes three basic steps: organic solvent extraction, delignification and alkaline hydrolysis. Recent works have suggested omission of the first step. We have made a detailed comparison in carbon isotope ratio of α-cellulose with or without organic solvent extraction using 32 consecutive tree ring and 30 subfossil peat samples. These samples were exposed to three different chemical treatments: with organic solvent extraction as the first step (CellOE), without organic solvent extraction (CellNOE), and with organic solvent extraction as the final step (CellNOE/OE). The third treatment is used to test if organic extractives can be completely removed or if their solubility in organic solvents has been altered by delignification and alkaline hydrolysis. In tree rings and peat, δ13CC ell NOE was always significantly different from δ13CC ell OE, but the trends were not the same. In tree rings, δ13CC ell NOE was always more negative than δ13CC ell OE by −0.31 ∼ −0.01‰. In contrast, δ13CC ell NOE in peat could be more negative or more positive than δ13CC ell OE by −3.08 ∼ 0.27‰. The third chemical treatment resulted in different patterns. For tree rings, δ13CC ell NOE/OE was still more negative than δ13CC ell OE by −0.36 ∼ −0.08‰. However, the differences between δ13CC ell NOE/OE and δ13CC ell OE for peat varied in a more narrow range from −0.58 to 0.61‰, compared to the differences between δ13CC ell NOE and δ13CC ell OE. These results exposed a complex chemical evolution behaviour and an incomplete removal of lipids during delignification and alkaline hydrolysis. The mean value, long-term trend and seesaw patterns for a tree ring or peat CellNOE series were significantly different from those for a CellOE series, indicating that omission of organic solvent extraction will lead to a biased inference of past environmental conditions.