Development of a simple recycling process for evaporated organic solvent after preparative supercritical fluid chromatography using powdered activated charcoal

In many drug discovery purification laboratories, solvent waste is often generated from the purification of compounds using preparative supercritical fluid chromatography (pSFC), which is considered a green technology. The resulting pSFC fractions containing the compounds of interest are evaporated, and distillates are usually discarded. In this study, a greener separation process was addressed by recycling the distillate using powdered activated charcoal (PAC). Adsorption behavior on PAC was studied for various classes of compounds in typical solvents used in pSFC such as methanol, ethanol, isopropanol and acetonitrile. Effects of vortexing versus flow-through methods were investigated. Results indicate that PAC adsorption is an effective method to remove most organic compounds in the aforementioned solvents. More than 99.9% of the four drug-like commercial compounds studied were removed from methanol using a ratio of 1 : 30 (compound : PAC) with the vortexing method in approximately 30 seconds. The flow-through method together with rotary evaporation using a ratio of 1 : 60, with a contact time of 10 seconds, was adequate for the removal of 49 out of a diverse set of 50 compounds. This process was successfully applied to reuse contaminated distillate from a previous pSFC purification by demonstrating the effectiveness of PAC in drug discovery labs.