Chemically Bonded Polyacrylamide via Thiol-Ene Click Chemistry as Separation Materials for Hydrophilic Interaction Liquid Chromatography

Thiol-ene click chemistry was applied to immobilize polyacrylamide onto alkenyl-modified silica to prepare a novel stationary phase for hydrophilic interaction liquid chromatography. Polyacrylamide was synthesized by reversible addition-fragmentation chain transfer reaction. Alkenyl functionalities were introduced onto the silica by the reaction of silica with the reaction product of 3-isocyanate opropyl trimethoxy silane, allylamine and pyridine in toluene to obtain alkenyl-modified silica (EUS, E-thiol-ene, U-urea, S-silica). The alkenyl-modified silica was then reacted with polyacrylamide in methanol at 55 °C for 48 h in the presence of 2,2-azo diisobutyl amidine hydrochloride to prepare a novel stationary phase (TE-UPAM, TE-thiol-ene, U-urea, PAM-polyacrylamide), for hydrophilic interaction liquid chromatography. This new stationary phase “TE-UPAM” was characterized by element analysis and infrared spectra, and the results showed that, compared with EUS, the carbon content of TE-UPAM increased and the characteristic peaks of multiple amide existed at 1636 and 1570 cm−1. The effects of water content, salt concentration and pH of the mobile phase on the retention time of polar compounds were investigated. The results showed that the retention time of polar compounds decreased with the increase of water content. In contrast with acidic polar compounds, the retention time of neutral and basic polar compounds increased with the increase of salt concentration, and the retention time of basic polar compounds decreased with the decrease of pH value in the range of 3.3–4.8. The novel stationary phase behaved better than traditional silica stationary phase in the separation of uridine and bases. In addition, good separation of oligosaccharides by the novel stationary phase was also achieved, indicating great potential in the separation of polar compounds.

Effective combination of “RAFT” and “click chemistry” is the greatest advantage of this paper. The preparation of a HILIC stationary phase (TE-UPAM) was based on strong hydrophilic polyacrylamide “grafting to” the surface of modified silica. After evaluation, the separation showed great potential application of this stationary phase.Figure optionsDownload as PowerPoint slide