Preparation Of Organically-inorganically Hybrid Strong Cation-exchange Monolithic Column For Liquid Chromatography Using Pre-alkenylated Silica Nanoparticles

A novel organically-inorganically hybrid strong cation-exchange monolithic column was prepared for liquid chromatography by in-situ polymerization of 3-sulfopropyl methacrylate potassium salt(SPMA)and pre-alkenylated silica nanoparticles(i.d.25-100 nm)in the presence of ternary porogen consisting of cyclohexanol,methanol and water in a 150 μm i.d.fused silica capillary.This column was named silica-nanoparticles-containing hybrid monolithic column(SHM column)hereafter.The preparation conditions for the SHM column were investigated and established based on SEM images and pressure-vs-flowrate curves with respect to the size of silica nanoparticles,porogen composition,total monomer concentration,organic functional monomer concentration and polymerization time.The selected preparation conditions were as follow: composition of polymerization mixtures,inorganic silica nanoparticles(14.4 mg),SPMA(3.6 mg),cyclohexanol(22.56 μL),methanol(7.52 μL),water(1.92 μL)and 2,2-Azobisisobutyronitrile(0.125 mg);polymerization time,7 h;polymerization temperature,60℃.Then,the SHM column was characterized in terms of the structural morphology,mechanical stability,permeability,swelling-shrinking behavior,binding capacity,column efficiency and preparation reproducibility.The results demonstrated that the SHM column has the advantages of no need for retaining frits,ease preparation and good reproducibility over packed columns,and is superior to the organic column in pore size,mechanical stability,resistance to swelling-shrinking and binding capacity.In comparison with the methods reported for hybrid monolithic columns previously,the present method for the SHM column is much simpler and the reaction conditions are milder and easier to control.Finally,the chromatographic performance of the SHM column was examined.Three monovalent inorganic cations were baseline separated based on strong cation exchange interaction and four nucleotides based on mixed-mode of hydrophilic and strong cation exchange interactions,exhibiting excellent performances.At the same time,the influence of the composition of mobile phase,pH value,ionic strength and content of ACN on chromatographic separations was investigated.