Calculation using internal standard

Hi there,
I want to calculate the amount with (single point-)calibration using an internal standard. However, the value in the "amount" field is not yet the actual amount, I think. The value should be multiplied by the weight of the internal standard to get a plausible result. If course, I have entered the weight of the internal standard as well as the weight of the reference standard using the button "Amount" during creation of the sample set.
Therefore I want to create a custom field which multiplies the "Amount" field with the weight of the internal standard. Unfortunately, I cannot find the weight of the internal standard for editing the formula in the custom field wizard.
Or did I something else wrong?

Thanks in advance!

Answers

  • I'm not sure what you are describing there but for internal standards usually you do the following: In the processing method, components tab, enter the names of the active component and the internal std component, with Retention time, RT window and Peak Match. Then in the row for your active, scroll across to the internal std column and pick the internal std peak here. Save all changes. Add any dilutions or sampleweights as required in the sample set. The next part depends on whether the concentration of the internal standard in your sample is the same as in your standards (so, for example, 0.5mcg/mL in both).


    If its the same, enter the concentration value for your active in the Value tab of your component editor for standards only and then switch to Standards and Unknowns view and put 1.00 against all your stds and unknowns for the Int Std peak.. If the concs are different enter these values as appropriate for standard injections. then when you process data the amounts will be calculated using the correct internal standard calibration of: (Y value of Active/Y Value of internal std*x value of int std Versus x value of Active).

  • I'm sorry I didn't make myself clear. But your explanation is very useful - many thanks!

    I wasn't aware I could change views between "Standards only" and "Standards and unknown". Now it`s clear!
  • question
    I need to report the calibration curve expressed by (Y value of Active / Y Value of internal std * x value of int std Versus
    Could Empawer 3 give me the graph of the curb?
  • You can add calibration curves using the report publisher, by selecting "Calibration Plot" from the tree on the left of Report Publisher. As long as you have assigned a peak as internal standard then you will get a curve displaying Area ratio on the Y-Axis (area of standard/area of internal standard *amount of internal standard) and the amount of standard on x axis.
  • I actually do the calculations as indicated, but when I use the "calibration plot" I get 2 logs one of my area asset per quantity and my internal area standard per quantity
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