小分子溶质-混合溶剂三元体系的优先吸附现象

介绍一种用差减色谱研究小分子溶质对混合溶剂中某种组分优先吸附的方法. 在该方法中,淋洗剂是混合溶剂, 进样试液由溶质溶于混合溶剂制得. 通过测定自由溶剂峰的尺寸, 得到优先吸附参数λ2 (λ2 为周围溶剂化溶剂中某种溶剂组分的超额量与溶质重量之比). 用该方法对由丙三醇与水-乙醇混合溶剂所组成的体系进行研究发现, 当混合溶剂中乙醇的质量浓度低于2%时, 丙三醇对溶剂组分的优先吸附可忽略; 当乙醇质量浓度达到5%时, 丙三醇对乙醇优先吸附; 当乙醇质量浓度在10% ~23%时, 丙三醇对水优先吸附; 当乙醇质量浓度在30% ~60%时, 丙三醇优先吸附的溶剂组分又变成了乙醇.

Preferential adsorption of a ternary system containing a small solute and a solvent mixture

A differential chromatographic method for studying the preferential adsorption of solvent components by a small-molecule solute dissolved in the solvent mixture is described. In this method, the solvent mixture is used as an eluent and a solute solution prepared by dissolving the solute in the same solvent mixture is used as the injectant. By measuring the size of the free solvent peak, the preferential adsorption parameter λ2, defined as the surplus weight of one solvent component in solvated solvent per unit weight of solute, can be obtained. The system of glycerol in a water-ethanol solvent mixture was investigated using this method. Preferential adsorption is negligible at concentrations of ethanol lower than 2% in the water-ethanol mixture. As the concentration of ethanol in the mixture increases, preferential adsorption behaves as follows: glycerol preferentially adsorbs ethanol at 5%, adsorbs water between 10% and 23%, and in the region of 30% to 60% adsorbs ethanol once again.