Two-dimensional wavelet compression of ion mobility spectra

A two-dimensional wavelet compression method has been developed as a tool for portable ion mobility sensors. Ion mobility spectrometry (IMS) offers chemical sensors with low detection limits and rapid response for many compounds. Two-dimensional wavelet compression yields compressions greater than 99% without significant loss of information. A method has also been developed and evaluated to optimize the compression. The compression method was evaluated with data acquired from two different ion mobility spectrometers: a Graseby chemical agent monitor (CAM) and a Barringer Ionscan® 350. Three different systems were used for the evaluations. The CAM detected vapors from mixtures of chemical weapon simulants of dimethyl methanephosphonate, diethyl methanephosphonate, and diisopropyl methanephosphonate. The Ionscan spectra were collected in negative ion polarity from HMX, an explosive, and positive ion polarity for benzoylecgonine, a metabolite of cocaine.