| Time-of-flight mass spectrometer(TOFMS)features simpler working principle,wide range of mass measurement,and relatively high resolution and sensitivity,which can obtain the whole spectrum information of the full mass range in a short time.Miniature MS has been used widely in the field of fast speed online detection for environment,process monitoring for chemical plant,clinical medicine and leak detection of industrial facilities.In this thesis,we mainly developed a miniature TOFMS based on the vacuum ultraviolet(VUV)photo ionization technology,and optimized the performance of the miniature TOFMS self-developed by our laboratory.The dimension of the instrument is 400×340×250 mm,weighs 17 kg,and has the detection mass range of m/z 15 to 500.The resolution is 843 at m/z 131,and the detection limit of benzene compounds and anesthetic sevoflurane can be up to the order of ppbv.In the photoelectron ionization(PEI)mode,the photoelectron under the action of electric field has an energy higher than 10.6 eV,and can ionize substances with higher energy.The PEI ionization source is not affected by water vapor and produces fewer ion fragments,and the molecular ion peak occupies the main position in the spectrum.A magnetic field enhanced photoelectron ionization(MEPEI)miniature TOFMS has been developed for point-of-care detection and verification the relationship between postoperative agitation symptoms and sevoflurane concentration in exhaled breath.The MEPEI is water vapor resistant and can directly ionize sevoflurane through capillary sampling and obtain its characteristic ion[C4H3F6O]+(m/z 181),and the analysis time of exhaled breath is only 60s.Three standard curves were formulated to quantitively detect sevoflurane in different scenarios,the coefficient of determination(R2)was higher than 0.9882 and the relative standard deviation(RSD)of signal intensity was only 1.24%.The results showed that four of the 46 children patients had agitation symptoms.The newly miniature MEPEI-TOFMS was also successfully used to evaluate the concentration of sevoflurane in medical environment.The real-time monitoring of sevoflurane concentration in exhalation indicates the potential of this method for low-cost and convenient point-of-care(POC)detection and diagnosis of agitation symptoms.A new method for leakage detecting of natural gas pipeline by miniature TOFMS,namely Ne Gas Tracer Method,was developed.In the experimental phase,Ne gas was detected by the optimized miniature TOFMS and it was directly divided into three concentration range:18-1000 ppmv,1000-20000 ppmv and 20000-300000 ppmv,with a quantitative curve correlation coefficient above 0.98 and RSD of 12.38%.The results fully met the requirements of the Ne gas trace method for natural gas pipeline leak detection experiments and miniature TOFMS was applied to the experimental site,the trend of the results obtained is completely consistent with the chromatographic results.The detection time of a single sample is only 60 s,and the presence of the main component CH4 in natural gas can be detected simultaneously.It also proves that natural gas and tracer Ne gas can be fully and evenly mixed,which further proves the feasibility of Ne gas trace method for natural gas pipeline leakage detection.This study is instructive for the fast and efficient leakage detection study of natural gas pipeline. |
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