High performance liquid chromatographic (HPLC) measures of hydrophobicity as determined by means of new HPLC columns.

Abstract

Two new commercially available reversed phase high performance liquid chromatographic (HPLC) columns were tested from the view point of their usefulness for determination of hydrophobicity by means of partition chromatography. One column comprised a specially prepared hydrocarbon-bonded silica stationary phase material. The other column was packed with a polybutadiene-coated alumina (PBCA) phase. As reference served a regular commercial octadecylsilica (ODS) column. A series of test solutes were pyrazine CH- and NH-acids--the compounds which are able to take part in specific as well as in nonspecific intermolecular interactions. Unique properties of the new hydrocarbonaceous column manifested themselves in regular linear relationships between logarithms of capacity factors and volume percent of methanol in aqueous eluent. The main advantage of the PBCA column is a possibility of performing chromatography at alkaline pH. Both new columns are superior to regular ODS columns in respect of providing reliable chromatographic measures of hydrophobicity. It was observed that hydrophobicity parameters determined in individual HPLC systems are not highly intercorrelated and hence can reflect different structural features of solutes.