Two-dimensional nonlinear wavelet compression of ion mobility spectra of chemical warfare agent simulants.

Ion mobility spectrometry (IMS) affords miniaturized hand-held devices that can be used for monitoring and remote measurement. Because such instruments have limits on storage capacity or bandwidth for wireless transmission, data compression is important. Furthermore, all instruments should be operated with the fastest possible sampling rates because a signal-to-noise gain can be achieved by wavelet compression. Linear wavelet compression (LWC) applied to IMS data may cause peak distortion when the spectra are reconstructed. Nonlinear wavelet compression (NLWC) precisely preserves the peak location (i.e., drift time), height, and shape. IMS data of three chemical warfare simulants, dimethyl methylphosphonate, triethyl phosphate, and dipropyleneglycol monomethyl ether, were collected from an Ion Track ITEMISER and a Graseby Ionics detector CAM. Two-dimensional NLWC was used to compress the IMS data in the drift time and data acquisition dimensions on IMS data of chemical warfare simulants. NLWC was applied to achieve a compression factor of 1/128 with relative error of root-mean-square of <0.25% in the reconstructed spectra. A method was also developed and evaluated for optimizing compression.