Enantioseparation of Mandelic Acid Enantiomers With Magnetic Nano-Sorbent Modified by a Chiral Selector

Abstract

In this study,R(+)-α-methylbenzylamine-modified magnetic chiral sorbent wassynthesized and assessed as a new enantioselective solid phase sorbent for separation ofmandelic acid enantiomers from aqueous solutions. The chemical structures and magnetic prop-erties of the new sorbent were characterized by vibrating sample magnetometry, transmissionelectron microscopy, Fourier transform infrared spectroscopy, and dynamic light scattering.The effects of different variables such as the initial concentration of racemic mandelic acid, dos-age of sorbent, and contact time upon sorption characteristics of mandelic acid enantiomers onmagnetic chiral sorbent were investigated. The sorption of mandelic acid enantiomers followeda pseudo-second-order reaction and equilibrium experiments were wellfitted to a Langmuir iso-therm model. The maximum adsorption capacity of racemic mandelic acid on to the magneticchiral sorbent was found to be 405 mg g 1. The magnetic chiral sorbent has a greater affinityfor (S)-(+)-mandelic acid compared to(R)-( )-mandelic acid. The optimum resolution wasachieved with 10 mL 30 mM of racemic mandelic acid and 110 mg of magnetic chiral sorbent.The best percent enantiomeric excess values (up to 64%) were obtained by use of a chiralpakAD-H column.