Chiral separations of mandelic acid by HPLC using molecularly imprinted polymers

Abstract

Styrene is used in a variety of chemical industries. Environmental and occupational exposuresto styrene occur predominantly through inhalation. The major metabolite of styrene is present in twoenantiomeric forms, chiral R- and S- hydroxy-1-phenyl-acetic acid (R-and S-mandelic acid, MA). Thus, theconcentration of MA, particularly of its enantiomers, has been used in urine tests to determine whetherworkers have been exposed to styrene.This study describes a method of analyzing mandelic acid using molecular imprinting techniques andHPLC detection to perform the separation of diastereoisomers of mandelic acid. The molecularly imprintedpolymer (MIP) was prepared by non-covalent molecular imprinting using (+) MA, (-) MA or (+)phenylalanine, (-) phenylalanine as templates. Methacrylic acid (MAA) and ethylene glycol dimethacrylate(EGDMA) were copolymerized in the presence of the template molecules. The bulk polymerization wascarried out at 4 o C under UV radiation. The resulting MIP was grounded into 25~441⁄4m particles, whichwere slurry packed into analytical columns. After the template molecules were removed, the MIP-packedcolumns were found to be effective for the chromatographic resolution of (±)-mandelic acid. This methodis simpler and more convenient than other chromatographic methods.