A comparison of extraction systems for plant water stable isotope analysis.
A comparison of extraction systems for plant water stable isotope analysis.
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DOI：
10.1002/rcm.8136
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发表时间：
2018-07
期刊：
影响因子：
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通讯作者：
C. Millar;D. Pratt;David J. Schneider;J. McDonnell
中科院分区：
文献类型：
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作者：
C. Millar;D. Pratt;David J. Schneider;J. McDonnell
水的稳定同位素比值（δ2 H和δ18 O值）已被广泛用于植物体内水分的示踪，用于各种生理、生态水文、生态地球化学和水文研究。在这种工作中，分析物必须首先从样品中提取，然后进行同位素分析。虽然低温真空蒸馏是目前文献中报道的最广泛使用的方法，但存在多种提取-收集-分析方法。尚未对植物组织进行正式的方法间比较。方法：我们进行了6种植物水提取技术的方法间比较：直接蒸汽平衡，微波提取，两种独特版本的低温真空蒸馏，离心和高压机械挤压。这些方法被施加到四个同位素独特的植物部分（头，茎，叶，根冠）的春小麦（小麦L.）。在可能的情况下，通过光谱（OA-ICOS）和基于质量的（IRMS）分析系统分析提取的植物水。春小麦生长在受控条件下与已知的同位素组成的灌溉输入。结果所测试的提取方法产生了明显不同的同位素特征。蒸馏，微波萃取，直接蒸汽平衡，高压机械挤压产生的水更丰富的2 H和18 O含量。低温真空蒸馏系统和高压机械挤压法产生的水更贫化2 H和18 O含量，这取决于提取的植物部分。各种方法也产生不同浓度的共提取的有机化合物，这取决于提取的模式。总的来说，直接蒸汽平衡法优于所有其他方法。结论：尽管低温真空蒸馏很受欢迎，但在挥发性有机化合物的有限共提取、快速样品通量和几乎瞬时返回的稳定同位素结果方面，直接蒸汽平衡法优于低温真空蒸馏法。现在需要对其他植物物种进行更多的研究，特别是木本植物，以了解这项研究的发现可以延伸多远。
RATIONALE The stable isotope ratios of water (δ2 H and δ18 O values) have been widely used to trace water in plants in a variety of physiological, ecohydrological, biogeochemical and hydrological studies. In such work, the analyte must first be extracted from samples, prior to isotopic analysis. While cryogenic vacuum distillation is currently the most widely used method reported in the literature, a variety of extraction-collection-analysis methods exist. A formal inter-method comparison on plant tissues has yet to be carried out. METHODS We performed an inter-method comparison of six plant water extraction techniques: direct vapour equilibration, microwave extraction, two unique versions of cryogenic vacuum distillation, centrifugation, and high-pressure mechanical squeezing. These methods were applied to four isotopically unique plant portions (head, stem, leaf, and root crown) of spring wheat (Triticum aestivum L.). Extracted plant water was analyzed via spectrometric (OA-ICOS) and mass-based (IRMS) analysis systems when possible. Spring wheat was grown under controlled conditions with irrigation inputs of a known isotopic composition. RESULTS The tested methods of extraction yielded markedly different isotopic signatures. Centrifugation, microwave extraction, direct vapour equilibration, and high-pressure mechanical squeezing produced water more enriched in 2 H and 18 O content. Both cryogenic vacuum distillation systems and the high-pressure mechanical squeezing method produced water more depleted in 2 H and 18 O content, depending upon the plant portion extracted. The various methods also produced differing concentrations of co-extracted organic compounds, depending on the mode of extraction. Overall, the direct vapor equilibration method outperformed all other methods. CONCLUSIONS Despite its popularity, cryogenic vacuum distillation was outperformed by the direct vapor equilibration method in terms of limited co-extraction of volatile organic compounds, rapid sample throughput, and near instantaneous returned stable isotope results. More research is now needed with other plant species, especially woody plants, to see how far the findings from this study could be extended.