Preparation And Characterization Of Photonic Crystal Stationary Phase And Its Application In Pressurized Capillary Electrochromatography

Photonic crystal is a novel material with regular packing structure and nanometer scale pore size.According to van Deemter equation,the smaller the particle size,the higher the column efficiency.With the particle of photonic crystal being uniform and arranged in the column regularly,eddy diffusion term can be decreased.In addition,nanochannels of sub-micron photonic crystals generate slipstreams that reduce the mass transfer and separation time and improve separation efficiency by reducing velocity distribution and peak broadening.Pressurized capillary electrochromatography(pCEC),using electroosmotic flow to propel the mobile phase,combines the dual separation mechanism of high-performance liquid chromatography(HPLC)and capillary electrophoresis(CE).Its plug-like flow greatly reduces peak broadening during chromatographic separation while not being limited by the backpressure within the column.The combination of pCEC and photonic crystals columns has a great advantage.Based on the above theory,the column formed by submicron photonic crystals combined with pCEC technology has a very high separation efficiency.It's likely to achieve the breabreakthrough improvement in the separation field.The performance of photonic crystal columns is closely related to the size,morphology and uniformity of the particles in the column.Due to the harsh requirements of periodic structure,the photonic crystal microspheres must be highly uniform as a photonic crystal structure unit.Monodisperse silica microspheres are one of the most studied and widely used monodisperse systems because of the controlled size and easy surface modification,which are mainly prepared by modified St?ber method,microemulsion method and seeded growth method.During the preparation process of microemulsion method,a large amount of added organic compounds can result in recycling difficulties,high cost,and environmental pollution.In this thesis,the factors affecting the preparation of monodisperse photonic crystal by modified St?ber method were investigated.The reaction conditions were determined by the size and morphology characterization.Finally,three kinds of monodisperse photonic crystal packing material were prepared.Subsequently,the influence factors of monodisperse photonic crystal materials prepared by seeded growth method were investigated,and the reaction conditions were determined by the size and morphology characterization.Three kinds of photonic crystal silica particles with larger size and good monodispersity were successfully prepared and C18 bonded on the surface.And they were applied to the separation of seven carbamate pesticides through pCEC platform.Finally,420 nm photonic crystal chromatography material modified by C18 silanization was packed into the capillary column.And hydroxypropyl-?-cyclodextrin was added to the mobile phase to achieve high resolution and simultaneous separation of Uniconazole,Diniconazole and Propiconazole.The thesis was divided into five chapters.The first chapter gave an overview of the basic theory and application of capillary electrochromatography,pressurized capillary electrochromatography,capillary column,capillary chromatographic packing material and pesticide research,and introduced the photonic crystal chromatographic packing material and its preparation methods in detail.In the second chapter,the effects of the concentration of ethyl orthosilicate,the concentration of ammonia,the temperature,the stirring speed and the post-treatment method on the size and surface morphology of the microspheres with modified St?ber method were investigated.They were characterized by scanning electron microscopy(SEM)and specific surface area measurement.Finally,a series of non-porous silica micro-particles with smooth surface and good monodispersity with particle sizes of 300 ± 5 nm,400 ± 8 nm and 500 ± 15 nm were synthesized under the control of various conditions.In the third chapter,the influence of adding method,adding rate,stirring speed and seed concentration on the particle size distribution of microspheres in monodisperse non-porous silica microspheres prepared by seeded growth method was investigated and evaluated by scanning electron microscopy(SEM)detection.Then,non-porous silica microspheres with smooth surface and good monodispersity were synthesized with the particle size of 600 ± 15 nm,700 ± 22 nm and 800 ± 23 nm.After modification with C18,a photonic crystal column was prepared.And 7 kinds of carbamate pesticides were efficiently separated on pCEC.The fourth chapter described the details of capillary column packed with modified silanization C18.By adopting this column and adding hydroxypropyl-?-cyclodextrin into the mobile phase,we successfully obtained the separation of 3 pairs of chiral triazole pesticide uniconazole,diniconazole and propiconazole on pressurized capillary electrochromatography simultaneously.The effects of chiral additive concentration,volume fraction of organic phase,applied voltage,concentration of buffer and pH value on the chiral separation were investigated.The optimized chromatographic conditions were as follows: 45/55(v/v)/ 20 mmol/L phosphate buffer(pH = 6.8)containing 20 mmol/L HP-?-CD;the pump flow rate was 0.04 mL/min;the applied voltage was-9.4kV;detection wavelength was 220 nm.Under the above conditions,the three enantiomers of enoxazole,diniconazole and propiconazole were separated simultaneously with the resolution of 4.20,12.9,4.41,4.09,1.70.The separation time was only 12 min and the separation efficiency was up to 310,000 plates/m.This study provided a new separation and analysis method for the simultaneous separation of chiral triazole pesticides and achieved better separation results.The fifth chapter summarized this research and looked forward to the possible research direction in the future.