SOLVENT STRENGTH MODEL FOR SUPERCRITICAL FLUID CHROMATOGRAPHY ON A POROUS GLASSY-CARBON STATIONARY PHASE

The results from extended studies of a porous glassy carbon (PGC) material for packed-column supercritical fluid chromatography (SFC) are reported. Low levels of organic modifiers are used to change the solvent strength of the supercritical carbon dioxide mobile phase. A linear model is developed describing solvent strength in terms of modifier molar volume, dipolarity, Lewis acidity, and Lewis basicity. The solvent strength in SFC PGC depends on the modifier molecular size as well as modifier polarity. Solute retention is controlled by molecular-level interactions in the following order of importance: dispersion > Lewis acid-base > dipolarity. The model was effectively used to choose a SFC mobile phase appropriate for analysis of selected polar acidic solutes.