Targeted isolations from complex samples using two-dimensional HPLC. Part 3 : a semi-continuous heart cutting mode at high sample loads

In this work the isolation of targeted components from complex mixtures was studied. Effectively this entailed increasing the peak capacity of both dimensions, which systematically allowed for an increase in sample load. The cost of increasing the peak capacity was at the expense of increased cycle time and increased solvent consumption, but improvements were gained in the recovery of the analyte and the purity of the final product. Increasing the peak capacity of the first dimension column resulted in the transfer of a less complex sample to the second dimension decreasing the separation demand in the second dimension, resulting in increased load capacity. It was clear from this study that maximizing the product purity, recovery, and production rate is a complex task; a task that is dependent upon the specific objectives of those undertaking the purification. This study, for example, showed that when the purity was maximized the practical production rate was lowest, whereas the highest practical production rate had the second lowest purity, while at the same time having the second highest total recovery. To maximize overall recovery 100% of the target should be transferred to the second dimension and this, in turn, yielded the second highest level of purity.