Identification Grading System
Bring the Power of Accurate Mass and Confidence to your Identification Problems
LECO's Identification Grading System (IGS) eases data review by allowing users to quickly see, justify, have confidence in, and report on which chemicals are in a particular sample. This in turn allows a user to make confident decisions on what to do next.
Start Knowing What is in Your Sample
The IGS uses all the available chemical information generated from the Pegasus® GC-HRT+ 4D to add confidence to your unknown unknown identification process.
The IGS gives a grade to a particular identification based on 4 criteria:
- Presence and accurate mass of a molecular ion
- Presence and good correlation of a spectral similarity score from a curated library
- Accurate masses of sensible potential formulae of fragmented ions corresponding to a spectral library hit
- Matching retention index from the library hit
The higher the value of the grade, the more confident you can be in your identification.
Theory of Operation
The true power of identification can only be realized with the combined power of GCxGC and high resolution time-of-flight mass spectrometry (TOFMS).
- GCxGC separates coeluting species and gives cleaner mass spectra than other techniques.
- TOFMS enables unskewed mass spectra across a chromatographic peak even across very narrow second dimensional peak; which, when combined with deconvolution, yields the highest quality spectra that you can generate.
Born out of the EPA’s Non-Targeted Analysis Collaborative Trial (ENTACT), the IGS is LECO’s solution to the time-intensive process of data review.
Take for example the unfiltered deconvolution results from a GCxGC-TOFMS analysis of a sample from the EPA's ENTACT project (below, left). By applying the IGS filter, we can quickly view only the most confident indentifications. This simplification is dramatic and enables you to immediately begin investigating the "unknown unknowns," as indicated by the arrows in the diagram image on the right.
Left: Initial HRD (n=4800). Right: IGS > 2 (n=245)
Of the known compounds entered into the sample from this particular example (which was provided to LECO as a blind sample), IGS identified approximately 80% of the known peaks. The combination of GCxGC and high resolution TOF was proven to be necessary for this confidence. Read "Identifying Small Molecules via High Resolution Mass Spectrometry" for more information.
Read more about how LECO utilized the Indentification Grading System in the EPA ENTACT Study:
Identification Grading System [PDF]