Capillary High Performance Liquid Chromatography (hplc) Heat Pump Heating And Gradient System Research

Mirco/nano-flow pump, as a key component part of capillary HPLC, has an irreplaceable role in the application of LC-MS, which can reduce the sample and solvent consumption, improve the detection sensitivity and increase the analysis speed. At present, micro-nano-flow pump with high accurate flow control under high pressure is still a challenging issue for researchers. In this context, thermal expansion pump (TEP) which utilizes the volume expansion of liquid in a heating chamber for fluid delivery is developed to achieve this technique. However, the development of TEM is limited by solvent gradient control and the thermal equilibrium of heating system. Herein, in this thesis, pump design and performance optimizationof TEP system were studied by focusing on the heating system and high accurate solvent gradient output at high pressure, and the research work is presented in four chapters.In Chapter1, the basic operating principles and the application of micro-nano flow pump in LC and HPLC, as well as the commercialization of relative technologies, were summarized. Besides, the development of thermal expansion pump for analysis in micro-scale was introduced, and finally, the background of this research was demonstrated.In Chapter2, a new type of thermal expansion pump using fused silica capillaryas heating chamber was developed. Based on the theoretical fluid delivery requirements, effect factors of TEPs, an overall design of heating system was completed, including the shape design and the material choosing of pump body and the pump support, the choosing of heating mode and the optimization of other conditions. In addition, we sieved the liquid medium used for TEP. When fused silica capillary was employed as heating chamber, water was superior to tetradecane and PEG-400by taking the thermal expansion property and viscidity into account. Meanwhile, by using direct heating mode controlled by a high precision PID controller, we successfully provided a pump which had accurate micro-flow and nano-flow output.In Chapter3, performances of TEPs with stainless steel capillaries of different sizes were investigated. By changing the heating chamber with stainless steel tubes, detailed work was done including research of the impacts of parameters of heating system on the flow delivery control, such as inner diameter and the thickness of the tube, heating mode and thermal-insulating treatment. The performance evaluation showed accurate flow output in a wide range from100nL/min-10μL/min at high pressure was achieved, which provided a basis for the design of micro-nano-flow ultra-high pressure liquid chromatography (μ-UPLC) system.In Chapter4, we put the TEPs into application and developed a gradient fluid delivery system. The system was composed by four independent thermal expansion pumps which were set in two groups, and the solvent output was controlled by three valves. There was a4port switching valve in each group, and the paralleled-set two groups were connected by a2position-6port switching valve to provide isolated outputs. By using this system, the interference of solvents could be prevented which should be attributed to the independent fluid delivery paths, and thus, more efficient gradient elution in sample analysis was available for users.