Ion mobility based instruments are widely used as detectors for explosives and illicit drugs. The key element in recognition of unknown substance is usually the peak position. Relative peak positions are generally used by employing a chemical standard to correct for instrumental errors and environmental changes. In the first part of this work, we reported that small displacements in the peak positions are observed which were attributed to Coulomb repulsion from neighboring peaks and cannot be simply corrected by using standard. It may cause false alarm or false negative. The peak displacements for several examples were carefully studied and a simple model was developed to derive a formula for correction of the peak positions. It was shown that the peak positions, td , needs to be multiplied by [1+?. td 2.( I /? t )(1- w /|? t |)], (for |? t |?w) where I is the intensity of the neighboring peak, ? t is its distance to the target peak and w is the peak width. ?is defined the peak-peak repulsion factor and can be determined experimentally. Another challenge in IMS-based detectors is inability is analysis of mixtures. Due to different ionization tendencies, some substances mask other substances. In the second part, we reported for the first time the coupling of the thin-layer chromatography and IMS. Varieties of different coupling schemes were tried. The schemes included; direct electrospray from tip of TLC strip, indirect electrospray from a needle connected to the TLC strip, introducing the moving solvent into the injection port and the simplest way, offline introducing scratched or cut pieces of strips to the IMS injection port. Acceptable separation was achieved for two component mixtures of morphine-papaverine, acridine-papaverine with TLC-ESI-IMS technique. For cutting TLC strips, a special injection port was designed to host the cut TLC pieces. With this method, identification of each spot on TLC was achieved by IMS in few seconds. Also, desorption from the TLC surface was done by laser and spark. In the third part, a thermal programmed desorption was used for separation of mixtures. Components in a mixture were separated in the injection port before introducing to the ionization region based on differences in their vapor pressure.
