Design and optimization of a corona discharge ionization source for ion mobility spectrometry

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Abstract
In this work the possibility of using corona discharge as an ionization source in ion mobility spectrometry has been investigated. The results for both positive and negative polarity in air are consistent with the Townsend formula which states that I/V is a linear function of V. The distribution profile of the corona ions has also been investigated and compared with that of the Ni63 ionization source. Generally, the total ion current obtained from the corona ionization source was greater than that of the Ni63 source by about an order of magnitude, which results in a better sensitivity and a higher signal-to-noise ratio. The positive and negative spectra of air were recorded and the positive spectra of acetone and dimethylmethyl-phosphonate were compared with that of Ni63. In the negative mode, a number of new peaks, apart from those of reactant ions, were observed which are mainly due to nitrogen oxides, formed by corona discharge. This problem was minimized by increasing the interdistance of the electrodes.