SUPERCRITICAL-FLUID CHROMATOGRAPHY - OPEN-TUBULAR VS PACKED-COLUMNS

This review covers the performance of open tubular and packed columns in SFC. Issues such as column dimensions, stationary phases, pressure drop, mobile phase gradients, injection and detection are considered. Further, the role of SFC in chromatography is discussed. Generally, open tubular columns are preferred for separations of complex mixtures, isomers and for eluting polar solutes with neat carbon dioxide. With current techniques high plate counts can be obtained, but analysis times are then relatively long. Although packed columns can give quite rapid separations, due to the pressure drop restriction, high plate numbers cannot be achieved. Universal detection is possible, also when polar mobile phase modifiers are used, with e.g. the evaporative light scattering detector and the mass spectrometer. The advantages of mobile phase composition programming are demonstrated.