High-performance liquid chromatographic analysis of free-base porphyrins : II. Structure effects and retention behaviour

Abstract

The high-performance liquid chromatographic separations, on 3-μm silica, of a variety of free-base alkyl porphyrins of the type isolated from sediments and petroleums, and of a number of their acetylated counterparts, have been compared. Members of pseudohomologous series and structural isomers of both aetioporphyrins and cycloalkano porphyrins are readily separable, although the method appears to be less effective for the separation of positional isomers. Substitution of a β-methyl substituent for a β-hydrogen atom results in an increase in t R, presumably partly as a result of increased basicity. The effect of the introduction of an acetyl substituent is to shorten t R in the cycloalkano components, despite the polarity increase, but to increase t R in the aetio components. The differences in t R are explicable, therefore, in terms of an interplay between basicity and polarity, brought about by changes in the structural features of the substituents. The availability of isolated components for coinjection provides a method for routine studies of the distributions of the components of sediments and petroleums.