%RSD of Reference and Individual Bracketing Custom Field

mguthrie
mguthrie
in Software Products
Hello,

I'm trying to come up with a custom field that can give me the %RSD of the retention time of initial reference injections and each bracketing (n=3) of each of the peaks. The problem I'm having is that if I have multiple bracketing injections, I can't separate them out to get the %RSD of just one bracketing with the initial reference. My sequence is similar to below:

Blank
Reference
Reference
S01
S01
S02
S02
Bracketing (1)
S03
S03
S04
S04
Bracketing (2)

What I have so far is R%.%..%RSD(Retention Time), but it includes both bracketing when I only want one or the other. Any help or ideas would be greatly appreciated!

Thank you!

Answers

  • Empower2019
    Empower2019
    There are two ways to do this. First, use the labels in the sample set to your advantage. Give the reference injections the same label in your sample set for example Ref or Reference, then do the same with the bracketing injections , example Bracket. Then alter your formula as such:

    SAME.%..%RSD(Retention Time)

    This will return the %RSD of retention time for injections which have the same label, so you will get one value for the 2 reference injections and a second value for the bracketing injections, which can be displayed in a report method by applying suitable filter criteria.

    If you cant change the labels, there is a second way around this but it involves making 2 CFs. 
    First, create a basic Sample, Text Custom Field called Ref. In the sample set, for the reference injections, enter a text like Ref in the Ref custom field, and for all the bracketing injections, enter text such as Bracket (you can N/A all the non-relevant rows in the sample set). Then create 2 Peak, Real CFs where you tell Empower only to look at the reference and bracketing injections:

    1. R%.%..%RSD((Retention Time*(EQ(Ref,"Ref")))

    2. R%.%..%RSD((Retention Time*(EQ(Ref,"Bracket")))

    This will return 2 different values when a result set is generated; first, a value for the %RSD of the reference injections and secondly a %RSD of the bracketing injections. 

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