Chapter 10 Mobile phases

TL;DR: In this article, the authors consider a repeated distribution of samples between two mutually immiscible liquids, where only the weak interactions of molecules occur because of dispersion forces, the values of activity coefficients may be expressed in values close to unity, where the main reasons for the inadequacy of the theory of solutions for giving an effective and sufficiently precise prediction of partition coefficients in any given system, a lack of data necessary for the prediction (molar volumes, critical temperatures and solubility parameters), and, to a certain extent, also the difficult calculations encountered.

Abstract: Publisher Summary In liquid–liquid chromatography, the fundamental process of distribution is based on dissolution. Hence, this technique may be looked upon as a repeated distribution of samples between two mutually immiscible liquids. The high efficiency of the distribution process may be achieved by a frequent repetition of the elementary distribution process affected by the movement of one liquid phase. The prerequisite for chromatographically utilizable sample retention in a liquid–liquid system is the achievement of a measurable concentration of solute in the mobile phase m and the stationary phase s. Deviations from the ideal behavior of the solute in solutions may be positive or negative and be of different magnitudes. In solutions, where only the weak interactions of molecules occur because of dispersion forces, the values of activity coefficients may be expressed in values close to unity. The main reasons for this are the inadequacy of the theory of solutions for giving an effective and sufficiently precise prediction of partition coefficients in any given system, a lack of data necessary for the prediction (molar volumes, critical temperatures and solubility parameters), and, to a certain extent, also the difficult calculations encountered.