Grafting of silica with a hydrophilic triol acrylamide polymer via surface-initiated "grafting from" method for hydrophilic-interaction chromatography

A novel hydrophilic polymer-coated silica sorbent has been prepared using the radical "grafting from" polymerization method through surface-bound azo initiators for hydrophilic-interaction chromatography (HILIC). The azo groups were introduced to the surface of silica gel through the reaction with amino groups on the surface of silica gel with 4,4'-azobis(4-cyanopentanoic acid chloride) (ACVC). The resultant azo-immobilized silica gel served as surface initiator to polymerize hydrophilic triol acrylamide monomer N-acryloyltris(hydroxymethyl) aminomethane (NA) in methanol to get hydrophilic polymer-coated silica sorbent. The obtained poly(NA)-coated silica (pNA-sil) was characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), and nitrogen sorption porosimetry (NSP). Then the pNA-sil was packed into the stainless-steel column and evaluated in high-performance liquid chromatography (HPLC). Good chromatographic performance for the separation of peptides and nucleosides was obtained under HILIC mode. The results indicated that the pNA-sil stationary phase behaved as mixed-mode retention mechanisms of hydrophilic and ionic interactions. Furthermore, the pNA-sil phase was used to separate tryptic digest of β-casein and our results showed that more than 12 peptides peaks were resolved and well distributed within the elution window. Finally, the pNA-sil stationary phase was demonstrated to possess remarkable reproducibility and stability. Taken together, the pNA-sil stationary phase prepared in the current study offers a potential application in proteomics study.