| Hydrophilic chromatography has stationary phase similar to normal phase chromatography and mobile phase similar to reversed phase chromatography.It has high value in separating polar substances.Compared with traditional packed column,monolithic column has better permeability and designability,but for hydrophilic organic monolithic column,the obvious disadvantage is that the column bed is easy to swell in organic solvent.Open tubular column is a special form of monolithic column,it has a perforated hollow structure and annular porous layer close to the wall of the tube,this enables the column to retain the characteristics of the monolithic column and allow a large flow of mobile phase to pass through,more importantly,the hollow structure enables the column bed not to be blocked due to swelling.Based on this idea,this paper attempts to explore the preparation and application of several hydrophilic open-tube monolithic columns,including three aspects:1.Using polyethylene glycol diacrylate(PEGDA)as monomer and ammonium sulfate as porogenic agent,ploy(PEGDA)open-tube monolithic column was prepared by simple aqueous two-phase polymerization.After optimization,the open-tube monolithic column with uniform polymer porous layer was obtained,and the column efficiency of 41500 plates per meter could be obtained by separating allyl thiourea at a flow rate of 1.8 mm/s.In addition,the column had a good separation effect on small polar compounds such as nucleosides and benzoic acids,and the separation mechanism is a typical hydrophilic retention mechanism.Especially,the five benzoic acid compounds could achieve the baseline separation within 5 min at 50 ~oC,indicating that the open-tube monolithic column had excellent selectivity for carboxylic acid functional groups.Finally,the gas chromatographic separation performance of the column was tested,and the separation ability was similar to that of PEG commercial column,indicating that poly(PEGDA)column had a wide application prospect.2.Based on ploy(PEGDA)monolithic column,methacrylic acid(MAA)was added into the reaction system,and the double bond reaction of PEGDA and MAA was utilized,poly(PEGDA-co-MAA)open-tube monolithic column containing both carboxyl and ether groups was prepared by thermally initiated radical polymerization.The monomer,temperature and other parameters were optimized in the synthesis of the open tubular monolithic column,and the column with uniform morphology and good permeability was obtained.The chromatographic separation ability of the column was investigated,and good separation results were obtained in the separation of polar substances such as nucleosides and phenols,the results showed that the polar compounds were retained as hydrophilic retention mechanism on the porous layer monolithic column.Compared with the ploy(PEGDA)column prepared in chapter 2,this column exhibited stronger hydrophilicity and better retention ability for nucleosides,benzoic acids and other substances.This column had a good separation ability for standards of tumor markers and chlorophenol environmental pollutants.3.On the basis of the first system,in this chapter,acrylamide(AM)was used as monomer and PEGDA was used as crosslinking agent,the ploy(PEGDA-co-AM)open-tube monolithic column containing both amide and ether groups was prepared.The optimized column had good permeability and could be used to baseline separate several polar molecules such as phenols and benzoic acids,and the column exhibited characteristicofhydrophilicretention.Comparedwith poly(PEGDA-co-MAA)column,the column still had a good separation capability for these polar small molecules with relatively low ACN content(80%)in mobile phase,moreover,the column had little change in the separation capacity after soaking in the acid and alkali mobile phase,indicating good stability.In addition,the column had a good separation ability for several tumor markers and chlorophenol environmental pollutant standard samples. |
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