Chiral separations in normal-phase liquid chromatography: Enantioselectivity of recently commercialized polysaccharide-based selectors. Part II. Optimization of enantioselectivity.

Earlier, a set of pharmaceuticals with different chemical structures has been used to evaluate the enantioselectivity of four recently commercialized polysaccharide-based chiral stationary phases, Lux Cellulose-1/Sepapak 1, Lux Cellulose-2/Sepapak 2, Lux Amylose-2/Sepapak 3 and Lux Cellulose-4/Sepapak 4 and of three Daicel columns, Chiralpak AD-H, Chiralcel OD-H and Chiralcel OJ-H, using the screening conditions of an existing generic separation strategy in normal-phase liquid chromatography (NPLC). In this study, the applicability of the optimization steps of the existing separation strategy was examined using 44 drugs (70 optimization cases) representing the three possible resolution situations that occur after screening. Optimizations are demonstrated by modifying parameters such as polar modifier percentages, temperatures, flow rates and additives concentration. Changing the percentage of polar modifier was found to have the largest influence on the resolution. The resolution, peak shape and the analysis time were nicely improved for 49/70 cases (70%) after the application of the original optimization steps. The introduction of some modifications to the original optimization increased this number from 49 to 62 cases, i.e. from 70% to 88.6%. Finally, an updated generic separation strategy in NPLC was proposed.