Management and control of modifier content in preparative SFC solvent cycles

The objective of this work was to establish a solvent cycle with a possibility for modifier control in a preparative supercritical fluid chromatography simulated moving bed plant (SFC-SMB). Fourier transform infrared (FTIR) spectroscopy and flame ionization detection (FID) have been investigated for measuring alcohol concentrations in supercritical carbon dioxide. The integration of these in-line techniques into a modifier control schema allowed the operation of a closed loop SFC-SMB cycle. The applicability of the developed control concept for usage of 2-propanol in supercritical carbon dioxide has been verified by an experimental test series involving an eight column SFC-SMB plant. Different process variations have been compared in terms of energy and solvent consumption. Hereby, savings of almost all CO2 and 76% modifier could be achieved.