Novel Triangle Scheme for Classification of Gas Chromatographic Phases Based on Solvatochromic Linear Solvation Energy Relationships

The purpose of this work was to apply linear solvation energy relationships (LSERs) with a new set of GC-based solute parameters (log L.¹⁸, π₂^,c, and α₂^c) to characterize and classify gas chromatographic stationary phases. The phases studied include the most representative phases, as identified by several chemometric methods, a variety of common capillary stationary phases, and a few new exceptionally basic hydrogen-bond-acceptor stationary phases. By use of a large number of test solutes, which span an extremely wide range in size, dipolarlty, and hydrogen-bond-donor and -acceptor strength, we have been able to define the dispersive, dipolar, and hydrogen-bond-acceptor strengths of the above phases. Solute retention on all phases is well correlated (r > 0.995) with quantitative scales of solute properties. The results of the correlational studies were substantiated by direct spectroscopic studies of the dipolarity of the stationary phases. The results indicate that there are no GC phases that are strong hydrogen-bond donors but there are many quite strong hydrogen-bond-acceptor (basic) phases. Thus it makes little sense, as has been done in the past, to use phase acidity as a classifying parameter. The results can be summarized in a novel type of phase classification “triangle” in which the apices represent the dispersive-cavlty, dipolar and hydrogen-bond-accepting properties of the phase, rather than the more conventional dipolar and hydrogen-bond-acceptor and -donor properties.