Qualitative analysis of trace constituents by ion mobility increment spectrometer.

Ion mobility increment spectrometry (IMIS) is a high sensitive selective ionization technology for detection and identification of ultra-trace constituents, including toxic compounds, CW-agents, drugs and explosives in ambient air or liquid sample. Like an ion mobility spectrometry (IMS), this technology rests on sampling air containing a mixture of trace constituents, its ionization, spatial separation of produced ions and separated ions detection. Unlike IMS, ions of different types in IMIS are separated by ion mobility increment, alpha. Value alpha, is a function of the parameters: electric field strength and form, atmospheric pressure. To exclude the influence of these parameters on an alpha, the method of explosives identification by a standard compound was suggested. As a standard compound iodine was used. The relationship among the mobility coefficient increments equal to the relationship among the compensation voltage alpha(i)/alpha(iodine)=U(i)/U(iodine) is determined, where i are ions of 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, p-mononitrotoluene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene This relationship is practically independent of the above mentioned parameters in the range 25<E/N<90 Td. The limits of the relative error of this relationship are determined both from spectra of individual compounds and nitrocompound-iodine mixtures.