GCxIMS Library Search

The GCxIMS Library Search enables the identification and characterization of unknown volatile organic compounds (VOC’s) in complex matrices. This cutting edge software tool makes optimum use of the gas chromatographic and ion mobility based (2-dimensional) separation in combination with the outstanding sensitivity of the IMS as detector at the same time.

Based on a NIST database of retention indices and the G.A.S. drift time library substance identification in GC-IMS-headspace analysis becomes easy and undoubtful.

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) [1], 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
• RI range variable by choice of compounds
• Included retention index libraries (NIST 2014 Retention Index database)
• Automated normalization of IMS drift times
• Includes IMS drift time library by G.A.S.
• Both libraries are editable and by that customized and extended by user
• Straight ‘Click-to-Search’ mode
• Search confinements e.g. by name fragments, included/excluded elements,    molecular weight, CAS number

 
[1] Kováts, E. Helv. Chim. Acta, 1958, 41 (7): 1915–32, doi:10.1002/hlca.19580410703