Corona Discharge Plasma In The Application Of Ion Mobility Spectrometer

The radicals and active spices produced by corona discharge plasma,especially,the superoxide anion O2-radicals with stronger oxidation play the important role in many physicochemical processes,which has been widely used as an ionization source.As a kind chemical process of atmospheric pressure separation,ion mobility spectrometry(IMS)has been the mainstream technology in explosives field detection and widely applied in airports and stations etc,so the development new ionization method to replace the radioactive ion source in IMS is highly demanded.In this paper,a novel negative corona discharge was developed for ion mobility spectrometer for rapid detection of trace explosives.Research corona discharge plasma on detection of explosives by IMS principle was carried out in this dissertation.Corona discharge ion mobility spectrometry(CD-IMS)has been conducted which was built on a novel structure of negative corona discharge plasma ionization source.The diameter of target electrode was 3 mm after the optimization which has a high performance for corona discharge.The reactant ions in the bidirectional gas flow mode and unidirectional gas flow mode were investigated by CD-IMS.The result showed that CD-IMS was running in the unidirectional gas flow mode to efficiently remove nitrogen oxides and ozone produced from the discharge process.The discharge voltage was 2400 V,the distance between the needle and the target electrode was 2 mm,the temperature of drift tube was 100℃ and the drift gas with flow rate was 1200 ml·min-1.Under the optimized conditions,the dominant reactant ions was O2-(H2O)n and could be used to directly detect the common explosives,such as trinitrotoluene(TNT),ammonium nitrate(AN),nitroglycerin(NG),pentaerythritol tetranitrate(PETN)and hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX)by CD-IMS.The difference of signal intensity in the bidirectional gas flow mode and unidirectional gas flow mode of CD-IMS was also compared and the result showed that the better sensitivity could be achieved in unidirectional gas flow mode.The limit of detection of TNT was achieved to 200 pg.These results indicate that the high sensibility,simple structure and no radioactive make the negative corona discharge plasma ionization source as a potential and promising ionization source for ion mobility spectrometry to detect explosives.