Preparation And Evaluation Of Organic-silica Hybrid Ion Exchange Monolithic Columns

Polyhedral oligomeric silsesquioxane(POSS)-based organic-silica hybrid monolith has obvious properties such as simple preparation,wide pH range and good solvent resistance,and has become a new research direction on hybrid silica monolith.In this paper,the fabrication of POSS-based hybrid monolithic columns with different ions was studied,and the separation performance of the resultant POSS-based monoliths has been evaluated for ion exchange interaction and hydrophobic/ion-exchange mixed-mode microfluid chromatography.The main research aspects are listed as follows:In chapter 1,literature review.The development of organic-inorganic hybrid silica monoliths and the progress of organic-inorganic ion-exchange hybrid column were summarized,and then the thesis basis and research scheme were put forward.In chapter 2,using the "one-pot" method,poly(EGMP-co-POSS-MA)column with surface-bonded phosphate ion was prepared by hot-initiating one-step polymerization with ethylene glycol methacrylate(EGMP)as monomer and methacrylic acid modified cage-like polyhedral oligomeric silsesquioxane(POSS-MA)as crosslinker.Various parameters including polymer composition,structure morphology and mechanical stability of the obtained monolith were studied,and the effects of mobile phases and separation voltage on the retention of charged ions were also investigated to explore the retention mechanism.Stable mechanical properties in different polar solvents and multiple retention modes such as reversed-phase chromatography retention and ion-exchange interactions have been well observed in poly(EGMP-co-POSS-MA)column,as can achieve good separation of hydrophobic benzene,positive charge nucleic acid bases and enkephalins.In chapter 3,poly(Ti4+-EGMP-co-POSS-MA)monolithic column was prepared by post-modification of Ti4+ ion onto poly(EGMP-co-POSS-MA)matix column.The parameters of post-modified reaction were optimized,and the energy spectrum analysis and electroosmotic flow characterization were carried out.The retention mechanisms of poly(Ti4+-EGMP-co-POSS-MA)column for different charged ions and p-phenylphosphonic acid were explored.The results showed that the prepared Ti4+modified POSS-based monolithic column was of stable mechanical properties,and the size of cationic electroosmotic flow was enhanced and the current direction was the same as unmodified phosphoric acid monolithic column.The retention of phenylphosphonic acid were enhanced and led to an increased resolution,as well as that of negatively charged benzoic acid compounds,positively charged nucleic acid bases and enkephalins.In chapter 4,poly(ZnA-co-POSS-MA)monolithic column was prepared via one-step polymerization by using zinc acrylate(ZnA)as monomer.The optimization of the column polymerization parameters,energy spectrum analysis and electroosmotic flow characterization were carried out.The prepared poly(ZnA-co-POSS-MA)monolithic column had enhanced hydrophilicity,stable mechanical properties,rich Zn2+ on the surface,and obvious energy spectrum analysis value.The effects of the retention of different charged ions and phenylphosphonic acid on poly(ZnA-co-POSS-MA)were explored.Polar phenol compounds showed good column efficiency.The phenyl phosphonic acid with phosphoric acid groups,nucleoside bases with primary amines and enkephalins had strong retention.Since the Zn2+ bonded monolithic column had strong retention on groups with phosphate ions,phenylphosphonic acid was eluted only under the condition of 0.1%ammonia high-strength elution.