Naringin-templated magnetic molecularly imprinted polymers for selective quercetin extraction from onion peel.

A Magnetic Molecularly Imprinted Polymer (MMIP) was developed using naringin as template molecule, acrylamide as functional monomer and polymerized by ultrasound irradiation for the adsorption of naringin. In an unexpected turn of results, the selectivity study unveiled that the synthesized MMIP exhibited a higher affinity for quercetin over naringin. Given this high selectivity, adsorption isotherm and kinetic studies were conducted for both quercetin and naringin. The adsorption isotherm indicated multilayer adsorption of the adsorbate on the adsorbent. The kinetic study showed better agreement with the pseudo-second-order kinetic model. The maximum adsorption capacity of 7.2 mg/g was achieved for quercetin at 50 mg/L and 4.9 mg/g was attained for naringin at the same concentration. Furthermore, quercetin quantification was performed by coupling MMIP with HPLC-UV, with method validation revealing the limits of detection (LOD) and quantification (LOQ) for quercetin. Additionally, agro-industrial waste onion peel, enriched with phenolic compounds such as quercetin, was subjected to solid-phase extraction using MMIP for the purification of quercetin.