Ionization of the Nitroaromatic Compounds in an Ion Mobility Spectrometer with an Ion Source based on Porous Silicon Under Laser Irradiation

Nowadays surface assisted laser desorption/ionization is widely used in different analytical methods. Some of the most interest methods are based on laser irradiation of nanostructured surfaces, porous silicon (pSi) in particular. This method already proved itself in mass spectrometry due to the combination of high sensitivity and possibility of investigation of small molecules because of the absence of the influence of a substrate on the ion signal. In this work we present summarized results of our investigations dedicated to the use of the surface assisted laser desorption/ionization on pSi in ion mobility spectrometry (IMS), which is one of the most promising analytical methods in the area of fast detection of low concentrations of organic molecules. We use trinitrotoluene (TNT) as a substance to be investigated. Obtained results show that TNT ionization mechanism under laser irradiation is complicated and relates both to the electron emission process from the pSi surface and subsequent ion-molecular reactions in gas phase and to the surface proton transfer as well.