基于PDMS的NMR中色谱技术的分离性能研究

Evaluation of Separation Performance of Polydimethylsiloxane-Matrixed Chromatography by NMR

以聚二甲基硅氧烷(polydimethylsiloxane,PDMS)作为NMR中色谱技术的虚拟"固定相",利用高分辨液体NMR中的DOSY技术考察其对正戊烷、1-溴戊烷和1,5-二溴戊烷这3种烷烃的分离性能.结果显示,在没有添加PDMS时,上述3种组分的扩散系数较接近,不能被分离;但当检测体系中含有PDMS时,3种组分的扩散系数相差较大,因而能被很好地分离.此外,还研究了样品温度和溶液粘度对分离性能的影响,其影响的趋势为:升高样品温度能改善混合物的分离;而增加溶液粘度则不利于混合物的分离.

Polydimethylsiloxane （PDMS） has been used as the virtual “stationary phase” （VSP） for chromatographic NMR. Its separation capability towards halogenated compounds was investigated. Diffusion coefficients ofn-pentane, 1-bromopentane and 1,5-dibromopentane contained in a mixture were measured with high-resolution liquid-state diffusion-ordered NMR spectroscopy （DOSY）. In the absence of PDMS, these diffusion coefficients were close, and as a result, the three components could not be separated. In contrast, the diffusion coefficients were markedly different from each other in the presence of PDMS, leading to excellent separation. In addition, the effects of sample temperature and solution viscosity on separation performance were also investigated. It was observed that separation performance improved as sample temperature rose; and reduced as solution viscosity increased.