Boronate decorated membrane via atom transfer radical polymerization for separation and enrichment of polyphenols from tea drinks

Boronate affinity (BA) materials play an important role in the selective separation and enrichment of cis-diol-containing compounds. However, a majority of BA materials suffer from low binding capacity and tedious preparation process. In this work, a novel high-capacity BA membrane was synthesized via a two-step procedure, including immobilization of active bromine groups on a nylon 66 membrane and grafting of poly(4-vinylphenylboronic acid) chains by surface-initiated atom-transfer radical polymerization. The successful synthesis was revealed by scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and so on. The BA membrane could not only selectively recognize cis-diol-containing compounds by specific interaction between cis-diol and boronic acid ligands, but also extensively adsorb non-cis-diol-containing compounds by hydrophobic (or π–π) interaction and B–O coordination effect. The novel BA membrane was used as an extraction material, and some parameters of extraction were optimized in detail. Membrane extraction coupled with ultra-high performance liquid chromatography was applied to the selective enrichment and determination of 10 kinds of polyphenols, including eight cis-diol-containing polyphenols and two non-cis-diol-containing polyphenols. The recoveries at three spiked levels from jasmine green tea were between 91.2% and 100.5% for cis-diol-containing polyphenols, with intraday and interday relative standard deviations ranging from 3.7% to 7.5% and 4.2% to 8.2%, respectively.