Instrumental Development And Key Techniques Of Miniature Ion Trap Mass Spectrometer With Continuous Atmospheric Pressure Interface

Miniature mass spectrometers(mini-MS)have broadened mass spectrometry analysis from conventional lab analysis only into in-situ areas,which is enabled by many key techniques for miniaturization of mass spectrometers.Of these techniques,atmospheric pressure interface(API)is a significantly more important one.Based on different APIs of membrane inlet and discontinuous atmospheric pressure interface(DAPI),there have been existed two types of miniature mass spectrometers correspondingly.These instruments have compact size,low power consumption,but also drawbacks in performances.So they are difficult to be used in harsh environment for analysis in real time.Therefore,how to break the barrier between portability and high performance has become one trend for the development of miniature mass spectrometers.This paper proposed continuous atmospheric pressure interface(CAPI)for miniature mass spectrometry for the first time,and developed miniature mass spectrometer with CAPI,which enabled continuous and efficient ion introduction being applied on a miniature mass spectrometer.Based on this instrument platform,some more key techniques related to the CAPI miniature mass spectrometer were also explored and developed,improving the analytical performances of the miniature system by further.Finaly,instrumental structure design was optimized and all components of system were packaged to an integrated instrumental entirety.In detail,the contents represented in this paper are listed as below:Firstly,a miniature mass spectrometer with continuous atmospheric pressure interface was developed.By calculation in theory,a differential pumping system was designed,and contributed to the development of a miniature mass spectrometer with CAPI,taking advantage of high pressure operation of an ion trap.This miniature mass spectrometer is sensitive and stable for sample analysis,owing to the fact that the analytical performance of this instrument independent on mechanical swtich control for the ion introduction.Besides,the system was able to rapidly analysis complex sample by coupling with various ambient ionization sources.This system would become a powerful tool for real in-situ analysis.Secondly,an sensitive in-vacuum plasma ionization source and aredynamic assisted sampling method were developed.Based on the theory of gas discharge,we designed a plasma discharge device inside the first vacuum chamber of the miniature mass spectrometer and optimized the system.This discharge ionization source improved the sensitivity of instrument for gas detection to ppb level.Besides,an aredynamic assisted sampling method was developed,further improving the detection distance for VOCs and the signal noise ratio(SNR).The achievements in this work made it is possible for miniature mass spectrometer to be applied to environmental pollution monitoring,detection of dangerous gas in public,danger checking in accident spots.Thirdly,we studied ion transmission theory and developed a mini ion funnel for miniature mass spectrometer.The techniques for efficient ion transmission were researched by means of ion trajectory simulations,hardware design and experimental proof.A mini ion funnel was developed and integrated into miniature mass spectrometer after optimizing its parameters of spacers and diameters.The mini ion funnel improved the sensitivity and mass resolution of instrument by over 20 and 2 fold respectively,which made the analytical performance of miniature mass spectrometer closer to the conventional io n trap mass spectrometer in lab-scale.Fourthly,atmospheric pressure matrix assisted laser desorption ionization(AP-MALDI)was employed and coupled into miniature mass spectrometer,which were able to direct analyze biological materials with high sensitivity and repeatability,including pepetides,proteins,tissue slicer,drugs in urine and blood,as well as rapid discrimination of bacteria.The study enabled the application of miniature mass spectrometer into point of care and rapid diagnose in hospital in future.Fifthly,we packaged the whole system of miniature ion trap mass spectrometer.Every part of instrument was optimized in further and integrated into one compact system.The integrated miniature mass spectrometer has small dimensions of 38×23×34 cm~3 and a weight of 10 kg,with high sensitivity of limit of detection of 10 ng/ml,rapid analysis speed of 5 Hz,wide mass range of 100-2000 Da,and capability of coupling with different ionization sources.By far,the miniature mass spectrometer with continuous atmospheric pressure interface has acquired the high analytical performance and portability in one system.