Construction Of Continuous Two-dimensional Capillary Electrochromatography System And Its Transport Characteristic Theory Research

Two-dimensional capillary electrophoresis, which combines two capillary columns with different separation mechanisms, can obviously enhance the peak capacity and conveniently adjust the selectivity. Continuous two-dimensional capillary electrochromatography, which directly connects two chromatography columns in series without interface, possesses the characteristics of easy operation and stability, which are important for the separation of complicated samples like natural products and proteomics samples, etc.Multiple continuous ion-exchange/reversed-phase capillary electrochromatography systems were constructed by using open-tubular column, packed column and monolithic column. Magnetic properties and huge surface area of magnetic nanoparticles coupled with magnetic field of external magnets were utilized to construct open-tubular capillary electrochromatography column with magnetic nanoparticle coating as stationary phase. Effects of column preparation conditions on system performances were investigated and constructed system was applied to the separation of traditional Chinese medicine and proteins. In two-dimensional capillary electrochromatography system, peak capacity, separation orthogonality and selectivity were adopted to evaluate the performance. Rhizoma gastrodiae and peptides were used as samples to investigate influences of different chromatography conditions like electric intensity, pH value, ionic strength and organic modifier on separation under isocratic and gradient elution, and further to evaluate the continuous two-dimensional ion-exchange/reversed phase capillary electrochromatography system. Effects of different length ratio of two dimensions or concentration ratio of mixed stationary phases on separation and influences of different species of solutes on retention factors were discussed to show the characteristics of continuous two-dimensional open-tubular capillary electrochromatography system and mixed stationary phases capillary electrochromatography system.Considering different generalized forces that solutes suffered in the two-dimensional capillary electrochromatography, transport equations of weak monoprotic acids in continuous two-dimensional capillary electrochromatography and transport equations of solutes in mixed stationary phases and continuous two-dimensional capillary electrochromatography under isocratic elution were obtained in theory. Based on them, transport equations of solutes in mixed stationary phases and continuous two-dimensional capillary electrochromatography under gradient elution were deduced in theory. Influence rules of separation field intensity, capillary (effective) length, pH value of buffer, ionic strength and organic modifer concentration on transportation of solutes were verified experimentally. Based on the transport equations of solutes in capillary electrochromatography with mixed stationary phases under isocratic and gradient elution, effects of ratio of mixed stationary phases on electroosmotic flow and migration rates of solutes and influences of ionic strength, organic modifier and pH value on retention times of solutes in capillary electrochromatography under double stepwise gradient elution were investigated, and it established the theoretical foundation for the development of analysis method in two-dimensional chromatography system.