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, op en tubular columns are preferred for separations of complex mixtures, isomers and for eluting polar solutes with neat carbon dioxide. With c urrent techniques high plate counts can be obtained, but analysis time s are then relatively long. Although packed columns can give quite rap id separations, due to the pressure drop restriction, high plate numbe rs cannot be achieved. Universal detection is possible, also when pola r mobile phase modifiers are used, with e.g. the evaporative light sca ttering detector and the mass spectrometer. The advantages of mobile p hase composition programming are demonstrated.