Identification of compounds is supported by matching both (GC & IMS) compound-specific separation properties. The gas-chromatographic retention times are normalized to retention indices (RI) , that are matched to literature- and database values. The software comes with a full non-restricted version of the NIST2014 Retention Index Database including NIST search software. The database includes ~400.000 annotated Kovats/Lee retention indices and ~83.000 compound entries. The ion mobility drift time (Dt) is a further specific parameter for a compound at constant measurement conditions. Potential measurement condition-based shifts are overcome in G.A.S. devices by normalization of Dt values when related to the reactant ion peak (RIP), which is directly accessible in IMS spectra in the positive polarization.
The search of unknown compounds is done by simply clicking on the respective signal peak in the GCxIMS chromatogram. The result is the listing of i) all library compounds with matching retention index and ii) a confined listing of compounds that match both retention index and IMS drift times. While the retention index match typically enfolds multiple compounds and a secured identification of the respective compound is hardly possible or only feasible if compounds can be excluded by plausibility. On the other hand, when IMS drift time entries are available, the matching list is confined drastically because the combination of the retention index, RI, and IMS drift time, Dt, is unique for a substance.
GCxIMS Library Search features:• System normalization by one measurement using a test mixture
 Kováts, E. Helv. Chim. Acta, 1958, 41 (7): 1915–32, doi:10.1002/hlca.19580410703