Esterified styrene-maleic acid copolymer modified silica as mixed-mode polymer-brush stationary phases for chromatographic separation.

Styrene-maleic acid (SMA) copolymer has received much attention for its excellent solubilization characteristics. In this work, SMA copolymer brush-based chromatographic stationary phases were exploited and developed for the first time. First, SMA copolymer brush was in situ grown on the surface of spherical silica via living/controlled reversible addition-fragmentation chain transfer (RAFT) polymerization method. Subsequently, as a proof-of-concept demonstration, the copolymer was esterified by diethylene glycol mono-2-ethylhexyl ether (DGME) and 2-(2-ethylhexyloxy) ethanol (EHOE), respectively. The obtained Sil-SMA-DGME and Sil-SMA-EHOE copolymer-brush chromatographic stationary phases were characterized by transmission electron microscopy, Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, and thermogravimetric analysis, respectively. The chromatographic retention mechanism indicated that both the two packed columns exhibited hydrophilic/reverse mixed-mode retention modes. The maximum column efficiency was up to 71,000 N/m. The chromatographic separation performance evaluation indicated that the novel kind of stationary phases had excellent separation capabilities for hydrophilic, hydrophobic compounds and phospholipid standards. In addition, by combination with mass spectrometry identification, the Sil-SMA-DGME column was further exploited for separation and identification of phospholipids in human lung cancer cells. Totally, 9 classes including 186 phospholipid species were successfully identified. The results demonstrated the promising application prospects of the novel kind of SMA copolymer-brush chromatographic stationary phases.