The thick syrup like CCDS samples were first centrifuged at 17000 g and 4°C for 15 min. Then 0.1 g of viscous supernatant was added with EC-d5 (10 µL, 10 ug/mL in water) and 0.2 mL of acetonitrile. Samples were vigorously vortexed for 30 s and then centrifuged. The supernatant (0.2 mL) was mixed with 0.3 mL of hexane and 0.3 mL of water. After top hexane layer was removed, 1 mL of MTBE and 0.1 g of NaCl were added to the lower layer, and the samples were vortexed for 1 min and then centrifuged at 2000 g and 4°C for 10 min. The top MTBE layer was recovered and dried down to ~100 µL.