Construction Of A Portable Quadrupole GC-MS And Development Of Its Circuit System

Gas Chromatography Mass Spectrometry(GC-MS)is a commonly used analytical instrument in laboratories.GC-MS combines the advantages of mass spectrometry with high detection speed,high detection sensitivity,and small sample volume with the separation function of gas chromatography to make the analysis effect Increased exponentially.Due to the excellent quantitative and qualitative capabilities of GC-MS,it is widely used in chemistry,chemical industry,military,criminal investigation,life sciences,pesticide residue detection,hazardous chemical detection and other aspects.In recent years,the demand for detection of Volatile Organic Compounds(VOCs)in the environment has been increasing.The analytical capabilities of GC-MS are very suitable for emergency detection of VOCs,but the conventional GC-MS in the laboratory is large in size and high in power consumption.Not suitable for on-site analysis,portable GC-MS came into being.Compared with the traditional GC-MS in the laboratory,portable GC-MS is small in size,light in weight,low power consumption,and fast in analysis speed.It is very suitable for on-site analysis.VOCs are tested.At present,the portable GC-MS market is almost monopolized by several foreign instrument companies.The domestic research on portable GC-MS started relatively late and relied on imported instruments for a long time.Facing the increasing demand for on-site analysis of VOCs,and in order to get rid of the dependence on foreign instruments,this paper developed a portable quadrupole GC-MS system.At present,the more mature portable GC-MS on the market are all based on the ion trap mass analyzer,but the space charge effect of the ion trap is obvious,which affects the accuracy of its analysis,and the hyperboloid of the ion trap is not easy to process.The quadrupole mass analyzer is effective in reducing the space charge effect,and the cylindrical electrode of the quadrupole is easier to manufacture and lower cost.Therefore,the portable GC-MS developed in this paper is based on the quadrupole mass analyzer developing.In this thesis,a portable quadrupole GC-MS was developed based on the on-site detection of VOCs.The key components of the chromatogram are selected and the chromatogram is designed and integrated using Solidworks software.The chromatographic gas circuit is designed,and there are different injection modes for analytes with different concentrations and different properties,including:(1)quick-check mode;(2)injection injection mode;(3)enrichment-desorption injection Mode;(4)Quantitative mode;(5)Backflush mode.The chromatographic column part adopts the low heat capacity chromatographic column technology,which can realize the rapid heating and cooling of the capillary chromatographic column,reducing the volume of the chromatographic column while reducing the power consumption and improving the analysis speed.The key components of the mass spectrometer were selected and the Solidworks software was used to design the mass spectrometer components and integrate the mass spectrometer as a whole.Including ion source ionization chamber design,tertiary ion lens and insulation design,filament selection and design;overall design of quadrupole mass analyzer,and SIMION 8.0 software was used to simulate the ion trajectory of the quadrupole;detector The selection of the medium multiplier and the design of the surrounding shield;the design of the quadrupole shielding cylinder and the detector shielding cylinder to reduce mutual interference between components and external interference;the design of the vacuum flange of the mass spectrometer makes the circuit inside the mass spectrometer The wire can be led out to the atmosphere;the combination of ion pump and getter pump is selected as the vacuum pump of the instrument,which reduces power consumption and volume;the method of pulse solenoid valve plus PDMS membrane is selected as the mass spectrometer injection interface,which reduces the input The sample volume maintains the vacuum of the vacuum chamber.Developed the power supply and control system for portable quadrupole GC-MS,used Altium designer design software to design the circuit schematic diagram and PCB of the system.Including a power supply board,a mass spectrometry control board,a chromatography control board and a bottom plate.The functions of the entire power supply and control system include: stable supply of electrical energy to all components and circuits of the portable quadrupole GC-MS,switching control of the ion source filament,ion lens voltage control,multiplier high voltage control,and mass spectrometry inlet control,The detection of the micro current of the ion pump,the vacuum protection of the ion source filament and the multiplier,the collection of the flow rate when the chromatogram is sampled,the heating control of the getter pump,the conversion control of the different gas paths of the chromatogram,and the key components of the chromatogram Temperature control,chromatographic injection flow control.The power supply and control system were tested.Soliworks was used to design the component placement and overall structure of the portable quadrupole GC-MS,and the complete instrument was built.The stability and resolution parameters of the instrument were tested with air and perfluorotributylamine standard samples.The results show that the long-term stability of the instrument is better than 1.128%,and the resolution is better than unit resolution.