Preparation And Evaluation Of A Novel Organic-inorganic Hybrid Zwitterionic Monolithic Column For Capillary Electrochromatography

A novel organic-inorganic hybrid zwitterionic ion-exchange monolithic column(shorted as pre-alkenylated silicagel hybrid column hereafter)is prepared by in-situ polymerization in a capillary with an internal diameter of 150 ?m.Using silicagel particles with a diameter of 10-20 nm(the surface is pre-alkenated)as crosslinkers.Methacrylic acid-N,N-dimethylaminoethyl(DAMA)and methacrylic acid(MAA)as functional monomers,The porogen is composed of water,cyclohexanol and methanol.Some main experimental factors,including the content of functional monomers,total monomer concentration,proportion of porogen,the time and temperature of polymerization are investigated and selected based on scanning electron microscopic images and the curves of backpressure vs flow-rate.Then,evaluation of the physical properties of pre-alkenylated silicagel hybrid columns,including the overall morphology of the stationary phase,permeability,ability to swell,mechanical stability and reproducibility.Experiment result show,compared with the previous organic monolithic column,the pre-alkenylated silicagel hybrid monolith have many advantages in performance.The stationary phase has the merits of less swelling-shrinking,more uniform pore sizes.Compared with the inorganic monolithic column,the preparation process of the hybrid column is simpler and has better reproducibility.In general,no post-modification treatment is required.Compared with the organic-inorganic hybrid monolithic columns reported previously,the present preparation method is much simpler.In addition,the hybrid column prepared in this experiment is filled with a stationary phase at both ends of the detection window.Compared with a conventional column-type electrochromatographic column,it can reduce the generation of air bubbles and improve the stability of the experimental operation.Due to the column surface possesses zwitterionic charge groups,the nature of the charge on the surface of the stationary phase and the size and direction of the electroosmotic flow can be adjusted by adjusting the p H value of the mobile phase,so that the column ion exchange mode is changed.The conditions such as p H value,competitive ion concentration,and organic additive content on the chromatographic separation performance of the mobile phase are optimized.A group of commom inorganic anions are separated based on ion-exchange mechanism and a group of organic amines are separated base on the mixed mechanism of ion-exchange and hydrophobic interaction.