A pseudo three-zone simulated moving bed with solvent gradient for quaternary separations.

Area of Science:

• Chromatography
• Separation Science
• Chemical Engineering

Background:

• Simulated Moving Bed (SMB) chromatography is a continuous separation technique.
• Solvent gradients can influence solute retention and separation in chromatography.
• Separating closely related compounds often requires advanced chromatographic strategies.

Purpose of the Study:

• To develop a pseudo-SMB method for separating medium-retained solutes from a quaternary mixture.
• To utilize selective solute trapping within a solvent gradient SMB system.
• To validate the method by separating capsaicin and dihydrocapsaicin.

Main Methods:

• A pseudo-SMB system was designed with specific solvent gradient conditions.
• Solutes were selectively trapped in designated zones (II and III) based on their retention.
• A quaternary mixture was introduced, allowing least and most retained solutes to be removed.
• Medium-retained solutes were subsequently recovered from the trapping zones.

Main Results:

• The pseudo-SMB method successfully separated two medium-retained solutes (B1 and B2) by selective trapping.
• Capsaicin (B1) and dihydrocapsaicin (B2) were effectively separated from a crude capsaicinoids mixture.
• Solute B1 distributed in zone III columns, while B2 spread in zone II columns, enabling distinct recovery.

Conclusions:

• The proposed pseudo-SMB chromatography with a solvent gradient is effective for separating medium-retained solutes.
• This method allows for the purification and separate recovery of target compounds like capsaicinoids.
• The technique offers a viable approach for complex mixture separations in chromatography.