Unknown Impurities Quantification

Hi, any body knows how to calculate unknowns impurities (not named at PM) if my criteria to reject peaks is based on [(Area/AverageMainPeakArea from all Stds)]*100.  I made some CF's like.  I have Empower 3...

CF_1 = S?.%..AVE(CCalRef1[Area]) - To get all Stds average area from main peak

CF_2 = CF_1*.0005 (to reject all areas below 0.05%) since LOQ = 0.05

Then I filter my peaks over 0.05 on the reports like: CF_2 >=0.05

My situation is that for unnamed peaks I can't get a result for CF_1.

In my processing method I'm using "RT Reference Used to Name Unnamed Peaks by RRT as my main peak).  I'm trying to get the results without Naming all unknown Impurities at the PM.

My final formula is CF_3: (Amount*2200)/(REPLACE(CConst3,1))

I get results for all my peaks with CF_3 but since I'm unable to get results for unnamed peaks for CF_1 and CF_2 I can't filter peaks over/under LOQ.

Cconst3 is the RRF

Thanks in advance,

Best Answers

  • Accepted Answer
    Hi, what does your final formula calculate? I presume its the final impurity calculation? If you are using amount then you are using the component editor and sampleweight/dilution fields to calculate amount? 

    I don't think you can calculate anything for unnamed peaks- you say that "My situation is that for unnamed peaks I can't get a result for CF_1.". But you need a named peak in order to populate CCalRef1, that cant be empty because that's what the formula is based on. Also, you could try to combine CF1 and CF2 into one simple CF:

    EQ(CCalref1[Area]*0.0005)*S?.%..AVE(CCalRef1[Area])

    That would give the average area of the CCalRef1 component in all standards labelled as S(?) but only for peak areas above CCalRef1 Area * 0.0005

    It looks like your CF3 multiplies peak amounts by a factor and divides by the RRF value of that peak, but the problem is if you don't have a named peak then the CConst3 field is meaningless, you don't have a peak connected to it and the only way to get that peak is to name it!

    I have had this issue before where I had a very large amount of impurities run over 100 minutes and two channels etc so naming each and every one would be impractical but the only alternative is custom fields but they must be very specific enough to calculate what you want without bumping up raw data and table space to impractical levels. 

    I would need more info on what the connection is with CF3 and CF1/2 before I could help. 
  • Accepted Answer
    The problem with this is you are expecting Empower to reject the area of an unknown and unnamed peak based on the average area of a named peak across the standards, and it doesn't work like that. 
    The way I would do this is keep your CF_1 for average area for main peak of standards. Then keep your CF_2 as well (CF_1*0.0005, call this CF Rejection Factor).
    Set up another Peak, Boolean custom field (called Test_Rejection_Factor), Use as Value, Search Order Result Set Only. Formula is GT(Area,Rejection_Factor) 0 = 0 and 1 = 1. 

    Then another Peak, Real, Calculated custom field (Final_Amount) of a formula:

    CF_3*Test_Rejection_Factor. This custom field will only give a result for CF_3 if is greater than the rejection factor, otherwise it will return 0. To get around the issue of unnamed peak, tick the box in the components tab of your processing method that says "assign unnamed peaks as RRT of active peak", that way all your peaks are now named along the lines of Unk RRT 0.765 etc.  Good luck!

Answers

  • Hi Emp2018, I really need a CF to reject areas below LOQ, including UnNamed Peaks so in the report I can use a criteria to group them....e.g. peaks below LOQ report < LOQ.  And for the peaks over LOQ I can use the CF_3 formula to report Releated Compounds.  But the area % for rejection is against the main peak average area from all stds.

    Thanks
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