Preparative high-performance liquid chromatography under isocratic conditions : I. Craig simulations for heavily overloaded separations

Craig simulations of preparative high-performance liquid chromatography were carried out for heavily overloaded separations as a function of the separation conditions (small-sample retention and column efficiency, sample size). These data were used to derive conditions for a maximum production rate (grams per hour) of purified product, and the results were compared with the treatment of Knox and. Pyper. There is an optimum sample size and column plate number for every separation; these optimum conditions are related to the desired recovery of purified product and to the retention (capacity factor, k′; separation factor, α) of a small sample under the same chromatographic conditions. Relative to the case of a 99.8% recovery of purified product from the feed, a 3-fold higher production rate is possible if sample size and column plate number are adjusted for 95% recovery of pure product; a 10-fold higher production rate is possible for conditions that give a 50% recovery of pure product. Teh required (optimum) plate number is halved on going from touching-band (99.8% recovery) separation to 95% recovery, and further halved for 50% recovery vs. 95% recovery. The maximum production rate also varies with sample retention ( k′, α for a small sample); a maximum value of α is preferred and k′ should be between 0.5 and 3.