Spiking Improved Solution Phosphorus-31 Nuclear Magnetic Resonance Identification of Soil Phosphorus Compounds
Spiking Improved Solution Phosphorus-31 Nuclear Magnetic Resonance Identification of Soil Phosphorus Compounds
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DOI：
10.2136/sssaj2008.0192
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发表时间：
2009-05-01
影响因子：
2.9
通讯作者：
Dougherty, W. J.
中科院分区：
文献类型：
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作者：
Doolette, A. L.;Smernik, R. J.;Dougherty, W. J.
利用P-31核磁共振（NMR）谱分析土壤有机磷的化学特性依赖于正确的共振赋值。我们研究了8种澳大利亚土壤，并通过将模型有机P化合物（α -和β -甘油磷酸、乙醇胺磷酸、植酸盐、六磷酸肌醇和磷酸胆碱）注入naoh -乙二胺四乙酸（EDTA）土壤提取物中，确定了主要的正磷酸盐单酯峰。对其中5种土壤，最强的单酯共振被鉴定为由于植酸盐，而对其他3种土壤，最强的共振被鉴定为由于α -和β -甘油磷酸。重要的是，以植酸为主的光谱和以甘油磷酸盐为主的光谱的外观是相似的，因为两个最强的植酸共振之间的分离与α -和β -甘油磷酸盐之间的分离非常相似。我们认为这可能导致在以前的一些研究中对这些物种的错误识别。由于它们的化学变化对pH值和电解质浓度的敏感性，阻碍了这些物种的鉴定。我们的增加方法，即我们只添加足够的化合物，大约是天然浓度的两倍，克服了这个问题。我们还研究了磷脂的碱性水解作为α -和β -甘油磷酸的可能来源。我们发现磷脂水解的速率取决于NaOH浓度，土壤提取物中甘油磷酸共振的存在可能是提取和再溶解过程的结果，而不是土壤中天然甘油磷酸的存在。我们还发现了一种中间二酯产物，可能以前被误认为是磷脂本身。
Chemical characterization of soil organic P using P-31 nuclear magnetic resonance (NMR) spectroscopy relies on the correct assignment of resonances. We examined eight Australian soils and identified the main orthophosphate monoester peaks by spiking model organic P compounds (alpha- and beta-glycerophosphate, ethanolamine phosphate, phytate, scylloinositol hexakisphosphate, and choline phosphate) into NaOH-ethylenediaminetetraacetic acid (EDTA) soil extracts. For five of the soils, the strongest monoester resonances were identified as being due to phytate, while for the other three soils, the strongest resonances were identified as being due to alpha- and beta-glycerophosphate. Importantly, the appearance of spectra dominated by phytate and those dominated by glycerophosphate were deceptively similar because the separation between the two strongest phytate resonances was very similar to the separation between the alpha- and beta-glycerophosphate resonances. We believe this may have resulted in the misidentification of these species in some previous studies. Identification of these species is hindered by the sensitivity of their chemical shifts to pH and electrolyte concentration. Our spiking methodology, in which we add only enough of the compound to approximately double the native concentration, overcomes this problem. We also investigated the alkaline hydrolysis of phospholipids as a likely source of alpha- and beta-glycerophosphate. We found that the rate of phospholipid hydrolysis was dependant on NaOH concentration and that the presence of glycerophosphate resonances in soil extracts probably results from the extraction and redissolution procedures rather than the presence of native glycerophosphate in the soils. We also identified an intermediate diester product that may have previously been misidentified as the phospholipid itself.