Preparation Of Core-shell SiO₂@SiO₂ Microspheres Using Polymerization-induced Colloid Aggregation Approach And Its Application In Fast Separation And Analysis By Liquid Chromatography

With the development of modem society and science technology,there are higher requirements on the high efficcy and rapid separation of complex samples to scientists.In recent years,it is the development of ultra high pressure liquid chromatography(HPLC)technique based on sub-2?m packing material and rapid separation technology based on core-shell microspheres that has made liquid chromatography technology enter a whole new eraof fast seperation.Surfacially porous core-shell microspheres with a high efficiency,high resolution and low back pressure have become the ideal tool for ultra fast liquid chromatography(HPLC)analysis,and have been applied to the rapid and efficient separation and analysis of complex samples successfully.However,there are still some problems in the preparation of core-shell SiO2@SiO2 microspheres,such as the complicated process,the wide particle size distribution and the uncontrollable thickness of the shell as well as the pore size and structure.Polymerization induced colloid aggregation(PICA)was previously used in the preparation of porous silica microspheres and has been used in that of core-shell silica microspheres in recent years.Although this method is simple,low cost and easy to enlarge,the synthesized core-shell particles have not only a poor monodispersity and a wide particle size distribution,but also a uncontrollable shell thickness and pore size,being vulnerable to the very common issues,that is,agglomeration and secondary nucleation in the preparation process,and consequently need a classification screening before using.In view of the above problems of PICA,we successfully synthesised the core-shell SiO2@SiO2 microspheres with controllable shell thickness and pore size by optimizing the experimental conditions in this paper,and further use them to the fast seperation of small molecules and biological macromolecules with a satisfactory results.This thesis mainly included the following research work:1.We synthesized core-shell SiO2@SiO2 microsphere using PTCA.The monodisperse modified nonporous silica was obtained without agglomeration by the reflux of neutral ethanol at the temperature of 80? with ?-ureidopropyltrimethoxysilane as the modifier.A series of parameters which can influence the rate of reaction,such as the pH value of the reaction system,temperature(T)and silica sol concentration(i.e.total volume of the reaction system)as well as the appropriate time to terminate the reaction(T)were optimized to successfully avoid the nucleation during the preparation process.The controllable preparation of SiO2@SiO2 core.shell microspheres with different shell thickness and pore size was achieved by adjusting the core/shell ratio and the particle size of silica sol.2,The SiO2@SiO2 core-shell microspheres with different pore size and shell thickness were modified by the octadecyl chlorosilane as reversed-phase chromatographic packing materials and further used to the separation of 6 kinds of aromatic alcohol homologues,6 kinds of benzene homologues and 6 kinds of proteins.The column prepared here with core-shell particles can achieve rapid separation of small molecules in 2 min and the separation of 6 kinds of protein within 1 min,respectively.The core?shell column with small pore size is suitable for the separation and analysis of small molecules;,and the larger pore size for macromolecular protein.In the separation of small molecule,shell thickness should be in 150?200 nm is appropriate,and the thickness of500 nm is more appropriate for the separation of protein.These results show that the SiO2?SiO2 core-shell microspheres prepared by PICA method can be used as a chromatographic matrix in the process of rapid separation and analysis.3.The prepared CS-C18 column with a pore size of 8 nm was coupled with the liquid chromatography-mass spectrometry technology and successfully applied to the fast separation of p-agonist in beef,melamine in milk and the chloramphenicol in honey.At the same time in the separation of puerarin in kudzu root extract is also achieved ideal results.The result showed that this CS-C18 column with a pore size of 8 nm is suitable to the rapid detection and analysis of small molecule solutes.The CS-C18 column with a pore size of 20 nm achieved an ideal result in the separation and analysis of protease hydrolysate,and it can be used in the the fast separation of polypeptide complex samples.The CS-C18 column with a pore size of 40nm was used to separate three of the proteins from egg white in 4 min,and this showes this kind of core-shell column are suitable for the rapid separation and purification of biological macromolecules.