Rapid method development for chiral separation in drug discovery using sample pooling and supercritical fluid chromatography–mass spectrometry

A novel strategy for rapid chiral method development has been implemented using sample pooling and supercritical fluid chromatography–mass spectrometry (SFC–MS) on four chiral stationary phases, namely Chiralpak AD and AS, and Chiralcel OJ and OD, and eight different modifier concentrations (5 to 40% methanol–0.2% isopropylamine). The screening is performed under an outlet pressure of 110 bar at 35 °C, and at a flow-rate of 2.5 ml/min for the initial 20 min and then ramped up to 4 ml/min and held for 4.5 min to elute all solutes from the column. The entire process is fully automated from injection to data processing, and operates unattended for 15 h overnight to obtain optimal chiral separation for multiple compounds. A unique feature of using SFC–MS to monitor chiral synthesis is the negligible interferences from achiral impurities. In addition, with SFC–MS, enantiomeric excess can be determined with much lower detection limits than UV and much shorter analysis times compared to normal-phase/reversed-phase liquid chromatography.