Empirical scheme for the classification of gas chromatographic stationary phases based on solvatochromic linear solvation energy relationships

Due to the plethora of materials that have been used as stationary phases in gas chromatography it is clearly necessary to have some method for classifying phases to facilitate systematic method development. The most popular classification scheme is the Rohrschneider-McReynolds procedure which is based on the Kováts retention indices of a variety of probe solutes. Although this is a very useful approach, it is highly empirical and has been criticized on several grounds. In this word we explored the use of solvatochromic measures of solute dipolarity-polarizability (π^*₂), hydrogen bond donor acidity (α₂) and hydrogen bond acceptor basicity (β₂) to classify a variety of common capillary gas chromatographic stationary phases. Preliminary studies show that the use of only the solvatochromic parameters as explanatory variables leads to rather poor precision. However, when log capacity factors on two extreme types of phases are included among the explanatory variables quite high precision, typically an average standard deviation of less than 0.07 log units, is obtained and all columns tested were easily classified. The two reference phases should be a low-polarity phase and a high-polarity, hydrogen bond acceptor phase.