Preparation And Characterization Of The Open-tubular Electrochromatography Column Based On Metal-Organic Frameworks

Open-Tubular capillary electrochromatography(OT-CEC)is a novel micro-column separation method developed two decades ago on the basis of capillary electrophoresis(CE)and high performance liquid chromatography(HPLC).With the advantages of the excellent selectivity of HPLC and the high efficiency of the CE,OT-CEC has developed rapidly and has been used in many fields,such as protein separation,chiral drug and biological sample analysis and so on.Due to several merits,including large specific surface area,easily adjusted channels and many metal active spot,MOFs have already gained the favor of the researchers,MOFs have been mainly employed as chromatography technology in the field of gas adsorption.CE column plays a critical role in the CEC as it directly affects the efficiency of sample separation and detection in the CEC,so seeking for a novel material is a key point to ensure the good performance of the column.Open-tubular capillary electrochromatography columns based on the ZIF-90 and ZIF-8 have been prepared and in which the MOFs have been used as the stationary phase in this paper.The performance of the electrochromatography columns was evaluated by the resolution of the PAHs.The main work of this thesis is as follows.Solvothermal method was adopted to prepare ZIF-90 and ZIF-8,and the prepared ZIF-90 and ZIF-8 were characterized by scanning electron microscopy(SEM),infrared spectrum analysis(IR),thermogravimetric analysis(TGA),X ray diffraction(XRD),and BET specific surface area measurement.SEM showed that the ZIF-90 prepared was of spherical with a uniform particle size of 2-5 μm;the prepared ZIF-8 is a regular 12-hedron structure with a particle size distribution of 1-6 μm.Characterized by BET,the crystal prepared were of larger specific surface area,the specific surface area of ZIF-90 was 662.78 sq.m/g and ZIF-8 was of 1106.77 sq.m/g;Characterized by XRD and IR,the prepared ZIF-90 and ZIF-8 crystals were consistent with the reported literature.The inner wall of the 100 μm quartz capillary,which is pretreated with Methane,Water and sodium hydroxide solution,was modified with APTES,then the prepared ZIF-90 was grafted to APTES.The prepared stationary phases in the inner wall of capillary was characterized by SEM,it can be seen that a continuous and dense ZIF-90 film was bonded on the inner wall of the capillary.8 kinds of PAHs,including naphthalene,acenaphthylene,acenaphthene,phenanthrene,anthracene,fluoranthene,pyrene,benzo anthracene were separated in the OT capillary grafted with ZIF-90 while Tris buffer solution containing an amount of acetonitrile.Several factors,such as pH of buffer solution,the concentration of Tris in buffer solution and the amount of the acetonitrile in Tris buffer solution was investigated.The experimental results showed that the 8 kinds of analytes were separated with the resolution ranged from 1.22 to 4.98 under 15.0 kV separation voltage and 2 s injection time,while 20 mmol/L Tris was adopted as buffer solution with 20% acetonitrile(v/v)and pH of 8.5.The durability experiment for one column showed no significant change in the resolution over 120 cycles of separation.The inner wall of the 100 μm quartz capillary,which is pretreated with Methane,Water and sodium hydroxide solution,was modified with APTES,then the prepared ZIF-8 was grafted to APTES.The prepared stationary phases in the inner wall of capillary was characterized by SEM,it can be seen that a continuous and dense ZIF-8 film was bonded on the inner wall of the capillary.8 kinds of PAHs,including naphthalene,acenaphthylene,acenaphthene,phenanthrene,anthracene,fluoranthene,pyrene,benzo anthracene were separated in the OT capillary grafted with ZIF-8 while Tris buffer solution containing an amount of acetonitrile.Several factors,such as pH of buffer solution,the concentration of Tris in buffer solution and the amount of the acetonitrile in Tris buffer solution was investigated.The experimental results showed that the 8 kinds of analytes were separated with the resolution ranged from 1.02 to 3.55 under 10.0 kV separation voltage and 3 s injection time,while 20 mmol/L Tris was adopted as buffer solution with 40% acetonitrile(v/v)and pH of 8.7.The durability experiment for one column showed no significant change in the resolution over 100 cycles of separation.