Substoichiometric NMR Analysis for Oxygen-containing Organic Compounds

提出了一种新的含氧有机化合物（000）亚化学计量核磁共振分析（SNMR）分析方法，该方法是基于顺磁性镧系（III） （Ln）螯合物作为移位试剂与OOC形成加合物。用溶剂萃取法研究了三（六氟乙酰丙酮）-铕（III）（Eu(hfa)_3）或-镨（III）（Pr（hfa)_3）与邻苯二甲酸二（2-乙基己基）酯（DEHP）、二甲基亚砜（DMSO）、聚乙二醇400）二甲醚（PEG）和聚氧乙烯（10）辛基苯基醚（TX100）等OOC的化学计量学和加合反应平衡。发现Ln(hfa)_3对PEG的加合物组成仅为1:1，对DEHP、DMSO和TX100的加合物组成仅为1:1和1:2，并确定了各自的加合物形成常数。通过核磁共振平衡分析，得到了加合物的形成常数和加合物中OOC质子的化学位移。这些知识导致了OOC的SNMR开发。通过对合成溶液中二甲基亚砜的测定，证明了SNMR方法的有效性。在DMSO样品溶液中加入亚化学计量量的Eu(hfa)_3，用NMR测定了甲基质子的化学位移。在样品溶液中加入一定量的二甲基亚砜后，测量化学位移，然后计算样品中二甲基亚砜的含量。DMSO的mM水平可以通过测量分析物的化学位移来确定，而不需要任何校准曲线。化学位移测量的重复性可达相对标准偏差的0.01%，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.