Development of Acid-Functionalized Molecularly Imprinted Phenolic Resin for Chiral Recognition of S-Venlafaxine

This article reports the synthesis of a molecularly imprinted phenolic formaldehyde resin for the selective recognition of the cationic S-enantiomer of venlafaxine. The resin was developed through the condensation polymerization of p-hydroxybenzoic acid (4-HBA) and 4-nitrophenol (4-NP) with formaldehyde in an acidic medium. The resultant polymer was reduced to introduce amino groups into the polymer to obtain a dual-functional resin with amino and carboxylic groups (CA-P). After the uptake of S-VF, glutaraldehyde cross-linking stabilized the resin and formed its enantioselective cavities. Adsorption studies showed that optimum conditions occurred at pH 7, whereas the maximum adsorption capacity was 420 mg/g according to the Langmuir isotherm. The selectivity coefficient of S-VF-IP was 13 times that of NIP, confirming that the imprinting process indeed occurred. Chiral separation experiments using the SV-imprinted polymer (S-VF-IP) column resulted in 98% enantiomeric excess for R-VF, whereas the respective NIP did not provide any enantioselectivity. These results show a great possibility of the developed resin in efficient enantioselective separation and offer a promising method for the purification of chiral drugs from racemic mixtures in pharmaceutical applications.