Preparation And Characterization Of Organic–inorganic Hybrid Silica HPLC Packings

Organic–inorganic hybrid silica materials have drawn a great deal of attention in the potential applications such as stationary phase for high performance liquid chromatography?HPLC?owing to their high mechanical strength,tunable pore structure and outstanding chemical stability.In this paper,organic–inorganic hybrid silicas HPLC packings were prepared via sol–gel and hydrothermal synthesis approach and polymerization-induced colloid aggregation method?PICA?by using silsesquioxane?1,2-bis?triethoxysilyl?ethane,BTESE?as precursor.The morphology,pore structure,hydrophobic property,thermal property and chemical composition of organic–inorganic hybrid silica particles were characterized by means of scanning electron microscopy,BET surface analyzer,X-ray power diffraction,elemental analyzer,thermogravimetric analyses,video-based contact angle system and nuclear magnetic resonance,respectively.Unbonding and C₁₈-bonded organic–inorganic hybrid silicas were used as HPLC packing materials and the chromatographic performance was also evaluated in detail.The unbonded organic–inorganic hybrid silica prepared by hydrothermal synthesis approach has a desirable spherical morphology with particle size of 2?m.The particles possess a hydrophobic inner surface and exhibit a surface area of 1136.40 m²g^-1,a pore volume of 0.39 cm³g^-1 and a pore size of 2.30 nm.Used as stationary phase for HPLC,the obtained material successfuly realizes a baseline separation of the mixture of uracil,phenol,pyridine,methylbenzene,ethylbenzene and tert-butylbenzene.The phthalate acid esters?PAEs?,a kind of pollutant,can also be baseline separated by this colomn.The materials retain more than 90%of their initial colomn efficiency after exposed for100 h to alkaline mobile phase,showing a high chemical stability.The chromatograms are highly repetitive.The silica can be successfully bonded with C₁₈ by co-hydrolysis and condensation method at an ODTES?octadecyltriethoxysilane?/BTESE molar ratio of 0.08.The C₁₈-bonded silica shows a desirable pore structure with a surface area of913.89 m²g^-1,a pore volume of 0.32 cm³g^-1 and a pore size of 2.43 nm.The material has a hydrophobic external surface with a water contact angle of 143.3±0.1°.Used as HPLC packings,the C₁₈-bonded silica indicates an enhanced column efficiency and symmetry of chromatographic peaks and an improved retention of the compounds.The organic–inorganic hybrid silica particles are also prepared by PICA method with a dodecyltrimethylammonium bromide?DTAB?/BTESE molar ratio of 1.2,a HCHO/Urea molar ratio of 1.2,and a pH value of 1.0.C₁₈8 is bonded into the silica by post-grafting method with an ODTES/[Si]molar ratio of 0.6.The obtained material exhibits a particle size of 2?m and a desirable pore structure with a surface area of97.36 m²g^-1,a pore volume of 0.25 cm³g^-1 and a pore size of 11.07 nm.The water contact angle on the C₁₈-bonded materials is 127.7±0.1°,showing that the material is hydrophobic.Used as HPLC packings,the particles successfuly realize a baseline separation of the mixture of uracil,benzene,methylbenzene,naphthalene and fluorine and show a high coloum efficiency.The chromatographic peaks exhibit relatively good symmetry,with a tailing factor of 1.002,1.002 and 1.008 for benzene,methylbenzene and naphthalene,respectively.