Why cant I get an Impurity Response for a group peak?

I run an impurity method which uses the Amount field as the impurity response. I also have 2 group peaks made up of A1 A2 and A3 for Impurity A, B1 B2 and B3 for Impurity B. Sometimes all the individual peaks of the group are present and sometimes only 1 or 2. 
My problem is i cant seem to get an impurity response for the Group peak..i get responses for the individuals but not the Group. I tried different iterations of the "Source of calibration" field in the Named Group tabs but its still blank. I double checked that i have values under the reporting threshold etc. I want to filter a peak table by "Above Reporting Threshold" equals Yes but since group peaks arent generating an impurity response, they are excluded from this criteria.
Any ideas whats going on? Maybe its not designed to calculate for Groups?


  • Hi again.  I think this needs to be done using a custom field.  Here are a couple of KB articles that might help.


    Good Luck!
  • Thanks for that Marc, that would help if I was using % Area and only had 1 group peak. The issue is, I need to set a few different reporting threshold for my group peaks and Empower 3 wont allow me to set a reporting threshold for a group peak. Is this typical with the Impurity function? It seems to only allow thresholds for individual peaks.. I wanted to filter a table by "Equals Above Reporting Threshold" of Yes but since I cant get a threshold for group peaks, I cant do it.
  • Before going all custom fields... please answer one dumb question:
    Did you tick the Group Peaks box in your report method's results table?
    By default, this is not checked...
  • Hi Dan yes i did but even before i get to the reporting stage, when im reviewing data there is no reporting threshold for any group peaks available to view in the review window. In fact you cant even pick a group peak as the main component in the impurity tab. 
    I tried the Group Impurity option to name my individual peaks based on component type but when i went to set a threshold on this, again group peaks were excluded. It seems the whole Impurity functions only apply to individual peaks which is flawed in my view. Many methods use group peaks in impurity methods.
  • Agreed. There are no available references for group anything, probably as a result of the amount of head scratching it would take to deal with RRFs and complicated threshhold rules that would be needed to do it properly.
    The easiest approach may be to deal with all of that individually and write a CF to sum certain peaks (I'd try to make the peaks of interest the same component type and sum based on that to make thinge easier).
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