Theoretical evaluation of the selectivity characteristics of gas-chromatographic stationary phases

Abstract

A theoretical approach is described and an evaluation of the selectivity characteristics of the statio- nary gas-chromatographic phases by the structural phase formula is carried out on its basis. The work is a continuation of the method developed by the authors for describing gas-chromatography stationary phases based on the theoretical method of describing intermolecular interactions in which the total energy of inter- molecular interactions is represented in the form of three components: polar, nonpolar forces and hydrogen bond. The proposed method of stationary phases classification differs from existing, mainly theoretical justi- fication, the lack of adjustable parameters and good predictive power; this method does not require special experiments or complex computer calculations, it is very economical to use experimental data. Selectivity is described by two relative characteristics - polarity and hydrophilic; polarity is the ratio of the square of the dipole moment of the stationary phase to its generalized charge and hydrophilicity, in turn, the probability of formation of a hydrogen bond.

Both these characteristics can be calculated from the information on the structural formula of the stationary phase. For most commercial stationary phases, the information on their composition is known, which makes it possible to evaluate the selectivity of these stationary phases, completely abandoning the evaluation experiment. The estimates are in good agreement with the results on the selectivity of commercial phases obtained by us earlier from the experimental data on the Kovacs indices; correctness of the methods is well demonstrated by the selectivity map (Fig. 4). This approach has a good predictive ability and can be used to predict the behavior of analytes in gas chromatography.