Application Of SNR Enhancement In Dielectric Barrier Discharge Low Temperature Plasma Mass Spectrometry

Dielectric Barrier Discharge Ionization(DBDI)is a new type of open atmospheric pressure mass spectrometry ion source.Because of its high ionization energy,reagent-free and easy to miniaturize,DBDI has been widely used in the field of rapid detection of drugs,chemical warfare agents,medicine and other fields,showing broad prospects for development and great application value.However,the high ionization energy of DBDI can easily lead to complex environmental background noise,which affects the signal-to-noise ratio of mass spectrometry detection.Therefore,how to suppress the background noise of DBDI environment and improve its signal-to-noise ratio of mass spectrometry detection is an important issue of general concern in the industry.Using ground electrode to suppress high-energy electronics technology can significantly improve the signal-to-noise ratio of DBDI mass spectrometry detection.At present,a large number of experimental studies have been reported.However,the research on its physical mechanism is rarely reported in the literature.Therefore,this paper uses numerical simulation and experimental application methods to study its mechanism and practical application,and ensures the reliability and stability of the experimental application platform by designing matching power supply.The research results are of great significance for further optimizing DBDI devices and guiding related experimental applications.It can be divided into three aspects:1.The numerical simulation method of DBDI cryogenic plasma fluid was established,and the mechanism and general rule of metal grid electrode in suppressing DBDI background noise were studied.The results show that the collision reaction of charged particles on the surface of metal grid results in a large amount of energy loss,so it has significant inhibition of electron and ion.In addition,the metal grid further widens the helium density layer downstream and reduces air doping in the working air,so it is an efficient background ion noise suppression technology.Through numerical optimization,it is found that the pore size of metal grid ranges from 0.2~0.4 mm,and better ion suppression effect can be obtained.2.An experimental application platform of metal grid DBDI-MS was built to study the enhancement effect of metal grid DBDI in mass spectrometry detection of some complex samples.The results show that the signal-to-noise ratio of mass spectrometry detection of Sudan III,isopropyl,PFOA and other samples has been increased by 5-6 times,which further improves the signal-to-noise ratio of DBDI in the detection of some complex samples.3.A new low-power high-voltage switching power supply with adjustable load power is studied.The results show that the discharge power of DBDI load can be effectively adjusted by adjusting the duty cycle of BUCK converter switch.The distortion rate of power output waveform is less than 1.44% and the power factor is higher than 0.97.It has the advantages of small size,strong load adaptability and high reliability.It provides a strong guarantee for the efficient and stable operation of DBDI in complex environment.