不同pH条件下典型有机磷核磁图谱差异性解析

doi:10.19894/j.issn.1000-0518.210001

摘要/Abstract

摘要：

液相磷-31核磁共振波谱技术（³¹P NMR）是当前国内外土壤有机磷（P_o）分子形态表征的主流分析技术，其主要利用乙二胺四乙酸-NaOH溶液提取，然后在高pH值（pH＝13）条件下采集谱图。然而，高pH值条件下P_o可能水解，同时鉴于实际土壤pH值通常在6～8范围内，因此有必要探究pH值对P_o核磁谱图的影响。对D-葡萄糖-6-磷酸（D-G-6-P）、5′-单磷酸腺苷（5′AMP）和磷酸二氢钠（NaH₂PO₄）标准品进行研究，溶解于一系列pH梯度的溶液中进行³¹P NMR测试和谱图解析。结果发现：pH变化显著影响供试化合物的核磁谱图，不同pH值显著改变D-G-6-P吸收峰的形状和位置；但主要影响5′AMP和NaH₂PO₄吸收峰的位置。D-G-6-P已被证明以α-和β-两种形态存在于溶液中。且在碱性条件下发生异构化或分解两种反应。部分磷酸葡萄糖异构化的产物是甘露糖磷酸和果糖磷酸，而在高pH值时超过50%的D-G-6-P分解，且主要以二羟基丙酮磷酸酯赋存；5′AMP在溶液中存在3种构象，因此主要存在一个三重峰，高pH环境下出现次生峰，可能是水解产生正磷酸盐的结果；而NaH₂PO₄受溶液pH影响，导致质子化程度不同，进而吸收峰位置改变。综上，常规高pH溶剂会改变某些P_o分子结构，所得的核磁谱图并非原样。研究结果对于深入理解基于核磁的P_o形态表征及开发实际土壤pH范围的核磁分析方法提供了参考依据。

关键词: 有机磷, pH, 溶液磷-31核磁共振波谱, 化学位移

Abstract:

Liquid phosphorus-31 (³¹P) nuclear magnetic resonance (NMR) spectroscopy is one of the major analytical technique for the characterization of soil organic phosphorus (P_o) species at the molecular level, and usually requires to extract soil P_ousing NaOH-EDTA (ethylene diamine tetraacetic acid) solution before the spectrum is collected under high pH (pH=13) conditions. However, soil P_omay be hydrolyzed under high pH conditions, which affects the accuracy of the P-NMR measurements. Furthermore, the pH of soils usually ranges from 6 to 8, and thus it is necessary to explore the differences in the spectra of P_ocompounds under different pH conditions. Typical P compounds including D-glucose-6-phosphate disodium (D-G-6-P), 5′-adenosine monophosphate (5′AMP) and sodium dihydrogen phosphate standards were selected for this study under different pH conditions. The results show that the pH change significantly affects spectral features of the investigated P_ocompounds. For D-G-6-P, the shape and peak positions of the NMR spectra both change under varied pH conditions, but pH mainly affects the position of 5′AMP and NaH₂PO₄absorption peaks. D-G-6-P has α-and β-forms in solutions, and transforms into glucose phosphate, mannose phosphate, fructose phosphate and saccharinic acid phosphate, but it mainly exists as 3-hydroxy-2-oxopropyl phosphate and saccharinic acid after degradation, accounting for more than 50% of the total content, at high pH. For 5′-adenosine monophosphate, there are three conformations of 5′AMP in the solution. The resolved peak at high pH probably results from the hydrolysis of 5′AMP to produce orthophosphate, while for NaH₂PO₄, the existence of and at low and high pH values leads to changes in the peak shift in the spectra. Overall, the extraction of P_ousing NaOH-EDTA solution with high pH may significantly change the speciation of P_o, and thus induce the changes in their spectra. This study provides theoretical bases for the comprehensive understanding of soil P_oNMR spectra and the development of new method to characterize soil P_o speciation at pH values approaching natural soil pH ranges.

Key words: Organic phosphorus, pH, Solution phosphorus-31 NMR spectrum, Chemical shift

中图分类号:

O627

赵宇航, 韩超群, 刘瑾, 夏星, 王艺皓, 杨建军. 不同pH条件下典型有机磷核磁图谱差异性解析[J]. 应用化学, 2022, 39(02): 315-321.

Yu-Hang ZHAO, Chao-Qun HAN, Jin LIU, Xing XIA, Yi-Hao WANG, Jian-Jun YANG. Investigation on the Spectral Variation of Typical Organic Phosphorus Compounds under Different pH Conditions Using Solution³¹P NMR Spectroscopy[J]. Chinese Journal of Applied Chemistry, 2022, 39(02): 315-321.

图/表 5

图1 不同pH值下5′AMP的NMR图谱

Fig.1 31P NMR spectra of 5′-adenosine monophosphate under different pH conditionspH：A.7.90；B.9.22；C.11.88；D.13.59

图3 D-G-6-P、5′AMP、KH2PO4，3种标准样品混合液在pH＝8.22与13.52下的磷-31核磁共振波谱图

Fig.3 31P-NMR spectra of D-G-6-P，5′AMP，NaH2 PO4，a mixture of three standard samples at pH values 8.22 and 13.52

表2 4种有机磷在不同pH值条件下δ的实际值与理论值比较

Table 2 Comparison of experimental and theoretical δ values of four types of organic phosphorus compounds under different pH conditions

pH	?	甘露糖磷酸	葡萄糖磷酸	果糖磷酸	5′-单磷酸腺苷
pH	?	Mannose phosphate	Glucose phosphate	Fructose phosphate	5′AMP
13.57～13.59	a	－	4.46	5.03	4.41
?	b	－	4.54	4.09	3.79
11.63～11.88	a	6.05	4.46	5.03	4.41
?	b	4.74	4.65	4.08	3.95
9.12～9.22	a	6.05	4.57	5.03	4.41
?	b	4.88	4.67	4.06	3.96
7.83～7.9	a	6.04	4.40	4.97	4.35
?	b	4.86	4.63	4.03	3.97

图2 不同pH值下D-G-6-P的磷-31核磁共振波谱图

Fig.2 31P NMR spectra of D-G-6-P under different pH conditionspH：A.7.83；B.9.12；C.11.63；D.13.57

表1 4种有机磷的δ与pKa值

Table 1 The δ and pKavalues of four types of organic phosphorus compounds

?	δ₁	δ₂	pK_a
6-p-D-Glucose	1.35±0.04	5.03±0.05	6.03±0.04
6-P-Fructose	1.09±0.03	4.46±0.03	6.06±0.02
P-D-Mannose	1.37±0.14	6.05±0.10	5.03±0.11
AMP（A 5′-P）	0.87±0.05	4.41±0.06	6.11±0.04

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