A Laser Desorption Ion-Mobility Increment Spectrometer for Detection of Ultralow Concentrations of Nitro Compounds

摘要

A compact instrument that implements for the first time a method for analyzing substances, in which laser desorption of analyzed molecules and laser ionization of an air sample are combined with the ion-mobility increment spectroscopy, is described. Pulse radiation of the fourth harmonic of a portable (2.6 kg) GSGG : Cr~(3+) : Nd~(3+) laser (λ = 266 nm) is used. The detection limit of the developed laser desorption spectrometer of the ion-mobility increment is 40 pg for trinitrotoluene (TNT), and the linear dynamic range for TNT is 0.1-20.0 ng. The results from detection of nitro compounds are presented: trinitrotoluene, cyclotrimethylene trinitramine (RDX), and octogen (HMX). It is shown that laser desorption of nitro compounds from a metal is accompanied by their decomposition on the surface and emission of fragments. An ion signal is obtained for nitro compounds that were ionized outside the spectrometer.