About qualifier ions
There are scenarios where you need to be absolutely sure about the presence or the absence of a specific compound. For example:
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Determine the content in a natural gas sample based on the distribution of different hydrocarbons
Confirm a compound's relative amount in a drug formulation
Examine an athlete's blood for a specific performance enhancing drug
Examine a food item for a pesticide residue
Qualifier signals are used to confirm the existence of a compound.
With Scan data: To find qualifier ions, Data Analysis extracts an MS spectrum for each peak in the Total Ion Chromatogram (TIC SCAN).
Spectrum extraction from TIC SCAN
The peaks in the spectrum can be different fragments, adducts, or isotopic peaks from the same compound or from different compounds.
The most abundant peak in the MS spectrum is considered the target. The second to nth largest peaks are candidates for qualifiers. Extracted Ion Chromatograms (EICs) are generated for both target ion and qualifier ions.
Extract EICs for target and qualifier
The EICs of target and qualifier ions are compared. A qualifier will be listed in the processing method if its retention time is within a given retention time window compared to the target signal. The qualifier will be listed as Passed in the injection results if its response is within a given range of response percentage compared to the target signal.
Comparison of target and qualifier
You set the number of qualifier ions, the acceptable retention time window and the required response percentage in the processing method (Compounds > Identification node., Qualifier Setup tab).
For details on qualifiers in SIM signals, see How Data Analysis finds MS compounds.