Definition of the Activity Coefficient for Polymeric Liquid Phases: Regression Equations for Retention Data of Homologous Series

Abstract

The current definition of the activity coefficient based on the mole fraction is found to give unsatisfactory values for polymeric stationary phases. A new definition is proposed which is independent of the molecular weight of the stationary phase, and can be used directly to obtain energies of mixing. Equations are presented for partition coefficients and specific retention volumes of n-alkanes on methyl silicones, and of n-alkanols on polyethlene glycols, relating them to the carbon number of the samples and the temperature of the column.