Empty entries in Constant file

Hi everyone

I’m working with OpenLab CDS v2.7 to create report templates.

In these programs, I’m trying to create a report template for an analysis of known and unknown impurities, which also uses as Constat file for several parameters.

Example of one of my Constant Files::

I want to create a CustomCalculation, which can determinate, whether the compound is a known impurity or an unknown impurity and use for all unknown impurities a response factor of 0.98.

Compound        Retention time                 Response factor

Compound_A  2.45       1

Compound_B  3.69       1

Known imp.A   3.38       1.2

Known imp.B   5.64       0.8

I want to create a CustomCalculation, which can determinate, whether the compound is a known impurity or an unknown impurity and use for all unknown impurities a response factor of 0.98.

  • You would need to have thresholds on retention times because the retention times you get from the software have a lot of digits and you will almost never land right on your retention time you define. For example, you can say your threshold is 0.05 minutes, then filter compounds by retention time is greater than or equal to the retention time - 0.05 and less than or equal to the retention time + 0.05.

    If you want it to give you a name from a retention time, you can do this in a nested if statement. It would be difficult to do this with a constant file unless you got very familiar with the functions that deal with lists and conversion. For most purposes, it would be much easier to hard-code these values into the report. If anything is on the table, you can also use the report script to do more complex operations without dealing with the list functions native to the report. That would probably be the easiest way, but I'm not sure if you are familiar and/or able to go that route.

    What do you want to do with the information once you have it? That will also change the best way to go about it. If you just want the name and RF, that's one thing. If you want to pull that compound into a table and do a bunch of calculations with it, that's something completely different.

  • Hello,

    Constants can only be retrieved by the compound name so they cannot be used for true unknowns. What you can do is in the CC where you retrieve the constants have an if statement to assign peaks that have no name (Len(Compound_Name) > 0 on the false statement) to your unknowns' value. The other option would be to create a timed group for the entire chromatogram that does not include knowns and then use that group name in the constants file. 

    Marty Adams

  • Hi,

    unfortunately, that’s not the solution to my problem.
    I have a result set with an unknown number of unknown impurities and want to calculate the amount of both the known compounds and the unknown impurities. So, I create an CustomCalculation, which uses a Constant file for several Parameters, including the relative response factors. My problem is that the result of the >getconstant(“”)< formula is empty, if the Compound is not listed in the Constant file (as stated it the documentation of the constant file) However I can’t create a CustomCalculation which triggers on an empty entry on the CustomCalculation file. Something like:


    if(getconstant(“Relative response factor”)>0, getconstant(“Relative response factor”),0.98)


    It is working for all listed Compounds, but not for any unlisted ones. Is there a way to work with an unlisted Compound?


    The only other option seems to create a large number of >unknown impurity #< entries in the constant file that can used as Compound_name, if needed.

  • Hello,

    Yes, that will not work. You need to test the length of the name as I said in the previous response. See the example below the unknowns have a low value of 1.56.

    if(LEN(Compound_Name)>0, getconstant(“Relative response factor”),0.98)

    Marty Adams

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