A separation strategy combining three HPLC modes and polysaccharide-based chiral stationary phases

Nine polysaccharide-based chiral stationary phases (CSPs) were used to define a separation strategy that combines normal-phase (NP), reversed-phase (RP) and polar organic solvent chromatography (POSC) modes. After limiting ourselves to two CSPs per mode, in total, five CSPs, Chiralpak AD (NP), Chiralcel OD (RP and POSC), Lux Cellulose-1 (NP), Lux Cellulose-2 (POSC) and Lux Cellulose-3 (RP), showed the broadest enantioselectivity and most complementarity. Six sequences of the three modes were considered to decide which sequence is the most successful for screening a set of 56 pharmaceutical compounds. Starting the strategy with the NP mode, followed by RP and finally POSC was found preferable from both the number of cumulative separations and of baseline separations. Two approaches were considered for strategy fine tuning using an additional set of eight racemic mixtures. In both approaches, seven of the eight compounds were baseline resolved, on one of the examined columns at either screening or optimization conditions of a mode. One approach was finally preferred because of its lower workload.