Application of Sub- and Supercritical Fluid Chromatography to Vanadium and Nickel Porphyrins

Abstract

Sub-and supercritical fluid chromatography using packed columns are applied for the separation of metallated tetraphenylporphyrins. Different stationary phases are examined in conjunction with 20% methanol-modified carbon dioxide. Results indicate that the C18 stationary phase is more selective for separation of porphyrinic derivatives compared with silica or phenyl stationary phases. Elution order of components appears to depend on the interaction of the metal center with the stationary phase. The chromatographic behavior of four nickel and vanadyl porphyrins is studied as a function of temperature (50 to 100°C) and pressure (3000 to 4000 psi). Increasing the pressure from 3000 to 4000 psi and maintaining a constant temperature of 75°C causes both resolution and peak width to decrease. Reasonable quality, yet not optimized, separations are obtainable at 50°C (subcritical) as well as at 100°C (supercritical) under a constant pressure of 4000 psi.