Weckwerth J D, Carr P W
Department of Chemistry, Kolthoff and Smith Halls, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455.
Anal Chem. 1998 Apr 1;70(7):1404-11. doi: 10.1021/ac9706739.
Linear solvation energy relationships were used to study the retention process in supercritical fluid chromatography (SFC) and to gain a better understanding of intermolecular interactions in supercritical fluids. Correlation of SFC retention data with a set of solute solvatochromic parameters, which are also applicable to gas and liquid chromatography, yields information regarding the relative contributions of dispersion, cavity formation, dipolar, and hydrogen-bonding processes to retention. Dispersion interactions and cavity formation processes dominate retention on an open tubular poly(dimethylsiloxane) stationary phase with pure carbon dioxide as the mobile phase. Dipolar interactions and hydrogen-bonding interactions are of decidedly less importance but do contribute significantly to retention. Based on prior solvatochromic studies of poly(dimethylsiloxane) and carbon dioxide, the changes in the regression coefficients with temperature and pressure are interpreted chemically. The relative importance of these contributions changes with temperature and pressure. As pressure increases, the carbon dioxide becomes more dense, and dispersion interactions between the solute and the mobile phase increase. A temperature increase at constant pressure decreases dispersion interactions with the stationary phase, as in gas chromatography, but also decreases dispersion interactions with the mobile phase, due to a decrease in carbon dioxide density. On the basis of the solvatochromic coefficients, carbon dioxide acts as both a Lewis base and a Lewis acid. The quality of fit for these correlations is very high and compares favorably with similar studies in gas chromatography and liquid chromatography, permitting the prediction of retention behavior from a solute's solvatochromic parameters.
线性溶剂化能关系被用于研究超临界流体色谱法（SFC）中的保留过程，并更好地理解超临界流体中的分子间相互作用。将SFC保留数据与一组溶质溶剂化显色参数相关联，这些参数也适用于气相色谱和液相色谱，可得出有关色散、空穴形成、偶极和氢键过程对保留贡献的相对信息。在以纯二氧化碳为流动相的开管聚（二甲基硅氧烷）固定相上，色散相互作用和空穴形成过程主导保留。偶极相互作用和氢键相互作用的重要性明显较低，但对保留有显著贡献。基于先前对聚（二甲基硅氧烷）和二氧化碳的溶剂化显色研究，对回归系数随温度和压力的变化进行了化学解释。这些贡献的相对重要性随温度和压力而变化。随着压力增加，二氧化碳密度增大，溶质与流动相之间的色散相互作用增强。在恒定压力下温度升高会降低与固定相的色散相互作用，如在气相色谱中一样，但由于二氧化碳密度降低，也会降低与流动相的色散相互作用。基于溶剂化显色系数，二氧化碳既作为路易斯碱又作为路易斯酸。这些相关性的拟合质量非常高，与气相色谱和液相色谱中的类似研究相比具有优势，从而可以根据溶质的溶剂化显色参数预测保留行为。
