Characteristic variations of gas-chromatographic retention indices for phases of variable composition

Abstract

On an example of mixtures of dinonyl phthalate and 2,2′-bis-(2-cyanoethoxy)diethyl ether, it was shown that the dependence of gas-chromatographic retention indices (RIs) on the composition (α) of mixed stationary phases can be both linear and with various abnormalities. These features of the dependence of RI-α can be explained by the existence of areas of homogeneity and disintegration of mixed phases. Another reason for the nonlinearity of the dependence RI-α is that the components of phases of variable composition are expressed in mole fractions, which is typical for polymethylphenylsiloxanes, widely used in contemporary gas chromatography. It is shown that the expression of composition in mass fractions enables the approximation of these dependencies in the homogeneity regions by linear regression equations with sufficient accuracy.