UTILITY OF THE DISPLACEMENT EFFECT IN THE ROUTINE OPTIMIZATION OF SEPARATIONS BY PREPARATIVE LIQUID-CHROMATOGRAPHY

The utility of the displacement effect, previously observed between the first- and the second-eluted components of a particular binary mixture ("sample self-displacement effect"), is demonstrated by a further series of experiments. The use of this phenomenon is shown to be an effective, general approach for the separation of a binary mixture. When practical, it considerably facilitates the optimization of experimental conditions for a high production rate of very pure fractions, while permitting the achievement of high recovery yields. Using a 750 x 21.4 mm I.D. silica column, separations of several two-component mixtures were achieved for loads as high as 6 g per injection. A good recovery of the first-eluting component with a purity higher than 99% is easily achieved. As the loading increases, tailing of the first component into the second band can reduce the production of the second component. Nevertheless, the recoveries for both components can be substantially greater than those achieved with conventional elution chromatography. Factors found to influence recovery yield are alpha, kappa' and the mobile phase flow-rate. Guidelines are presented that can be used routinely to induce the self-displacement separation mode.