Substoichiometric NMR Analysis for Oxygen-containing Organic Compounds

提出了一种新的分析含氧有机化合物(000)的亚化学计量核磁共振分析方法。该方法是基于顺磁性稀土(III)(Ln)络合物作为位移试剂与OOC形成的。用溶剂萃取法研究了邻苯二甲酸二乙基己酯、二甲基亚砜、聚乙二醇400二甲醚、聚氧乙烯辛基苯基醚等有机有机化合物与tris(hexafluoroacetylacetonato)-europium(III)(Eu(hfa)_3)或-Pr(HFA)3的化学计量比和形成加合物的平衡。结果表明，Ln(HFA)_3的加合物组成对聚乙二醇只有1：1，对DEHP、DMSO和TX100分别为1：1和1：2，并测定了它们的形成常数。通过~1H核磁共振的平衡分析，得到了加合物的形成常数和OOC质子在加合物中的化学位移。这一知识导致了针对OOC的SNMR开发。通过对合成溶液中DMSO的测定，验证了SNMR的有效性。在DMSO的样品溶液中加入亚化学计量的Eu(HFA)3，用核磁共振方法测量了甲基质子的化学位移。在样品溶液中加入已知量的DMSO后，测量化学位移，然后计算样品中DMSO的量。仅通过测量分析物的化学位移即可确定DMSO的毫米级，而无需任何校准曲线。化学位移测量的重复性好于0.01%的相对标准偏差，测定值的精密度和准确度很高。

A novel analytical method of substoichiometric nuclear magnetic resonance analysis (SNMR) for oxygen-containing organic compounds (000 has been proposed The present method is based on the adduct formation of a paramagnetic lanthanide (III) (Ln) chelate as a shift reagent with OOC. The stoichiometry and the equilibrium of the adduct formation of tris(hexafluoroacetylacetonato)-europium(III)(Eu(hfa)_3) or -praseodymium(III) (Pr(hfa)_3) with OOC such as di(2-ethylhexyl) phthalate (DEHP), dimethyl sufoxide (DMSO), poly(ethylene glycol 400) dimethyl ether (PEG), and polyoxyethylene(10) octylphenyl ether (TX100) were studied by the solvent extraction method. The composition of the adducts of Ln(hfa)_3 was found to be only 1:1 for PEG and 1:1 and 1:2 for DEHP, DMSO, and TX100, and the respective adduct formation constants were determined. From the equilibrium analysis by 'H NMR, the adduct formation constant and the chemical shift of OOC protons in the adduct were obtained. This knowledge led to develop SNMR for OOC. The validity of SNMR was demonstrated by the determination of DMSO in a synthetic solution. A substoichiometric amount of Eu(hfa)_3 was added to the sample solution of DMSO and the chemical shift of the methyl-protons was measured by NMR. After a known amount of DMSO was spiked to the sample solution, the chemical shift was measured, and then the amount of DMSO in the sample was calculated. The mM level of DMSO could be determined by only measuring the chemical shift for the analyte without any calibration curves. The repeatability of the chemical shift measurement was as good as 0.01% as relative standard deviation, and the precision and accuracy for the determined values were very high.