Unspecidied impurities calculation

Hi,

I have created a CF for the calculation of unspecified impurities.   

CF=Amount/CCalref1(Std_Dilution)/CCalRef1(Label Claim)*100

 Calculation of unspecified impuritiesis done against  a standard.  Default peak is tick (for the component used for calculation), sample type and peak type is set to All.  Std Dilution and Label Claim are inputs.  CCalRef1 is a specified impurity

Calculations are working fine when the CCalRef1 is present in the sample injection.  But if the CCalRef1 is missing in the sample, Empower does not give any results.  Amount is calculated however. 

Any clue??

Answers

  • Is the peak in CCalRef1 the same one used as the default peak? If so, default peaks are mandatory peaks and when they are missing in a chromatogram, any calculations where CCalRef1 is referenced wont work.
    If its just not working when CCalRef1 is not present, you need to adjust the formula using REPLACE, which replaces missing peaks or fields with a numerical value or another custom field. You need to tick Missing Peaks in the custom field editor for this to work. 
    What do you want to replace CCalRef1 with? As an example, use 1 which will allow the CF to calculate. Your formula then becomes:
    Amount/REPLACE(CCalRef1(Std_Dilution),1)/REPLACE(CCalRef1(Label_Claim),1)*100. This will yield Amount/100 for samples where CCalRef1 is missing. You can replace the values with 0 or other CFs too, depending on your needs. I couldnt type square brackets around Std Dilution or Label Claim, using a mobile phone!
  • Thanks for the quick answer!

    In my case, CCalRef1 is use also as the default peak. 

    So if the default peak is present is the standard but missing in the sample injection, I won't be able to use the CF for calculation?  But Empower is able to calculate an Amount, what is exactly the difference?
  • It calculates amount because the curve generated by the default peak is used to generate an amount value for the unspecified peaks. But because CCalRef1 isnt present, then the values for Std Dilution and Label Claim wont mean anything and the CF crashes out.

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