Core-Shell Metal-Organic Frameworks/Molecularly Imprinted Nanoparticles as Absorbents for the Detection of Pyrraline in Milk and Milk Powder.

A novel core-shell metal-organic framework coated with a dummy template molecularly imprinted polymer (MOF@DMIP) was synthesized by one-pot bulk polymerization for the detection of pyrraline in food samples. The pyrraline analogue pyrrolidine-3-carboxylic acid was used as the template because of its lower cost, and MIL-101 was used as the MOF core owing to its numerous inherent advantages, including high chemical and hydrothermal stabilities. MIL-101@DMIP was used to detect trace pyrraline in foods by solid-phase extraction combined with high-performance liquid chromatography. It exhibited the advantages of faster mass transport, excellent sensitivity, and selectivity. Under optimum conditions, the detection limit of this system was 40.7 μg L-1, and a linear range was from 5 × 10-7 to 2 × 10-3 mol L-1, within relative standard deviations of 4.46-6.87%. The recoveries ranged from 92.23 to 103.87%, indicating the excellent ability of the prepared MIL-101@DMIP to recognize pyrraline in complex food matrices and its potential for application in pyrraline detection.