Dopant-enhanced atmospheric pressure glow discharge ionization source for ion mobility spectrometry

A dopant-enhanced atmospheric pressure direct current glow discharge ionization source for ion mobility spectrometry (APDCGD-IMS) has been described. It is shown that the ion intensity can be greatly increased by addition of species with ionization energy lower than that of buffer gas when the direction of the electric field between the target electrode and the extraction electrode was opposite to that of the drift field. With N(2) as the buffer gas, adding O(2) (or air), acetone, and CH(2)Cl(2) with certain concentration can enhanced the ion intensity more than one order of magnitude, and for O(2), it was found that the enhancement depending on both the concentration of O(2) and the flow rate of the carrier gas, and the largest enhancements of the signal intensity for electron in negative mode and reaction ion in positive mode reached at O(2) concentration about 1.5%-2%. The main physicochemical processes were summarized and discussed, and a zero-dimensional reaction rate model was set up to simulate the corresponding results. It was proposed that the enhancement of signal intensity was ascribed to the various ionization processes and reactions in APDCGD.