Research On Key Technologies Of Portable Gas Chromatography-quadrupole Mass Spectrometer

The portable gas chromatography-mass spectrometer(GC-MS),an important field detection and analysis instrument,plays an important role in the field of biochemical warfare agent detection,emergency response,explosive detection,and environmental monitoring.According to the difference of mass analyzers,the portable GC-MS can be divided into two types: quadrupole and ion trap.Compared with the ion trap mass spectrometer,the quadrupole mass spectrometer has the advantages of strong quantitative ability and good repeatability,which make it more favored.However,the only mature product in China is portable gas chromatography-ion trap mass spectrometer,and the domestic market is almost monopolized by foreign portable gas chromatography-quadrupole mass spectrometer.To meet the increasing market demand,break the monopoly of foreign technology,and improve the research and development level of the mass spectrometer in China,it is of great significance to develop a portable gas chromatography-quadrupole mass spectrometer.In this thesis,the key technologies of portable gas chromatography-quadrupole mass spectrometer were studied,and a portable gas chromatography-quadrupole mass spectrometer with small volume,low power consumption,and fast analysis speed was developed.Firstly,the basic structure of portable GC-MS was studied,and the whole frame structure of the portable gas chromatography-quadrupole mass spectrometer was designed.Next,the key technologies of chromatography were studied.This thesis completed the working principle and structure design of the chromatographic part.The gas inlet and split/non-split inlet were combined in the chromatographic part,which made it possible to analyze samples in a variety of matrices,such as gas,liquid,and solid.Meanwhile,the chromatographic part included pre-concentration injection,quantitative loop injection,and split/non-split injection mode,which could realize sample analysis in an ultra-wide concentration range of ppt～ppm.The separation part adopted a low thermal mass chromatographic column,which could realize rapid temperature rise and fall,and the fastest heating rate could reach 143.27°C/min.The system composed of the designed chromatographic part and conventional time-of-flight mass spectrometer had a good separation effect and repeatability in the detection and analysis of four-component benzene series and TO15 mixed standard gas under different injection modes.Then the key technologies of mass spectrometry were studied.Simion 8.1 software was used to construct the miniaturized EI ion source structure,and the ion trajectories and focusing states in different EI ion source structures were compared to complete optimization of the miniaturized EI ion source structure.The dimension design and function verification of the quadrupole mass analyzer size were completed by the combination of theoretical calculation and simulation of SIMION 8.1 software.The design of the vacuum chamber and the selection of vacuum pumps were completed according to the size of the ion source,quadrupole,and detector.Preliminary performance tests were performed on the mass spectrometer with perfluorotributylamine after construction,and the results showed that the mass spectrometer could analyze ions in the range of 40～300 amu and achieve unit mass resolution.Finally,the construction and preliminary performance test of the prototype were completed.The whole machine adopted modular design and construction.Firstly,the chromatograph,mass spectrometer,and circuit control parts were assembled separately,and then the parts are assembled to complete the whole machine construction.The prototype,with a size of 42×42×20cm and weighing 18 kg,could be operated continuously for more than 2 hours under the battery power supply,which meets the requirements of field detection for portability and high analysis speed.The preliminary performance test results showed that the developed prototype could realize the detection and analysis of 20 ppb benzene series composed of benzene,toluene,chlorobenzene,and p-xylene.And 1ppb toluene sample could also be detected with a 26:1 signal-to-noise ratio.