Peak ratio calculation

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Hello,

I have a dilemma on a peak ratio calculation.

In my sample set I have these two lines :

1. STANDARD SOLUTION define as Standard. (Contain compound A and B where A is the Internal standard that I also add in the sample solution)
2. SAMPLE SOLUTION define as Unknown (contain compound A and B)

This is a ISTD and the compound A is present in both solutions.
In my processing I have set the compound A as Internal standard.

Here's the calculation I'm having trouble with:

(Area of compound B in SAMPLE SOLUTION / Area of compound A in SAMPLE SOLUTION) / ( Area of compound B in STANDARD SOLUTION / Area of compound A in STANDARD ON)

Is there any way to calculate this in EMPOWER 3.6 0 ?
And without using Label is this also possible ?

Many thanks !


Maxime.
The best way to do this is an intersample custom field. If you label the standard as S and the sample as U, and create a Peak, Real custom field with a formula:

U.%.(Response)/S.%.(Response) and set the search order to Result Set First. Make sure that Peak type and Sample type are set to All. Process a sample set to generate a result set and the result will populate for the unknown sample.

Response is the Empower field which calculates Area of Active/Area of Internal Standard.

I dont think there is another way for Empower to do this without using a CF.
Hello,

Thank you for your quick response, however I may have been too brief on my example.

In reality I have to calculate my batch with the average of the injections of "standard 2" in the first part of my sample set.
In addition, I must use three vials in order to generate these three injections. (GC)
I call them :
- Standard 2.1
- Standard 2.2
- Standard 2.3

Can I use the Summary function AVG() in order to calculate my batch ?
Her is a screenshot of my sample set to illustrate.

Thank you for your time.
Image
Hi and thanks for the further info.
Yes you can do this by labelling your 3 standards as S1 S2 and S3 then label your Batch samples as U1, U2 etc.
Change the formula to U%.%.(Response)/(S%.%..AVE(Response)) and change search order to Result Set Only.
You also must put the function Summarize Custom Fields as the last line in sample set, and ensure this line is set to Normal.
Then, process a sample set to generate a result set, where the values for each of the Batch samples will be calculated for this custom field.
I don't get this. Isn't it just a normal one-point internal standard calibration?
If you define the concentrations of A and B in the standard as both "1", and set up an internal standard calibration, one point, linear, forced to the origin, then the calibration curve is y=mx+c where c is zero and m is the slope, and x=1. Since y is the peak area ratio of the two chemicals, the calibration curve is y = (Area of A in std/Area of B in std).
The samples get read off this calibration curve, reading the point where y = (Area of A in sample/Area of B in sample) = (Area of A in std/Area of B in std) * x, where x is the concentration reported by the usual processing. That means that the concentration reported is indeed (Area of A in sample/Area of B in sample) divided by (Area of A in std/Area of B in std), which is what you wanted.
EmpowersBane wrote:
Hi and thanks for the further info.
Yes you can do this by labelling your 3 standards as S1 S2 and S3 then label your Batch samples as U1, U2 etc.
Change the formula to U%.%.(Response)/(S%.%..AVE(Response)) and change search order to Result Set Only.
You also must put the function Summarize Custom Fields as the last line in sample set, and ensure this line is set to Normal.
Then, process a sample set to generate a result set, where the values for each of the Batch samples will be calculated for this custom field.


Thanks you for your response @EmpowersBane !
It does work very well !

I will finally be able to get rid of my excel sheets... 8)

lmh wrote:
I don't get this. Isn't it just a normal one-point internal standard calibration?
If you define the concentrations of A and B in the standard as both "1", and set up an internal standard calibration, one point, linear, forced to the origin, then the calibration curve is y=mx+c where c is zero and m is the slope, and x=1. Since y is the peak area ratio of the two chemicals, the calibration curve is y = (Area of A in std/Area of B in std).
The samples get read off this calibration curve, reading the point where y = (Area of A in sample/Area of B in sample) = (Area of A in std/Area of B in std) * x, where x is the concentration reported by the usual processing. That means that the concentration reported is indeed (Area of A in sample/Area of B in sample) divided by (Area of A in std/Area of B in std), which is what you wanted.


I tried to do this kind of calculation but I did not manage to get the expected results.

I'm not used to (first time) using the internal standard in EMPOWER, are there any subtleties that I missed ?
Something specific in the processing method maybe ?

To me, EMPOWER succeffully calculate the peak ratio (with the field Response and I saw it in the Review window when I display the field) but I can't manage to use the Reponse which I get from my sample and then divide it by the Reponse from my standard.
There is another way to do this without custom fields. Keep the labels for the standards as S1,S2 and S3 and your unknowns U1,U2..etc. Then set up lines in your sample set after your batch samples: Clear Calibration, Calibrate with a Label Reference of S* and Quantitate with a Label Reference of U*. Then in your processing method, for the component in which you want an internal standard, pick the component from the drop down column called Internal Standard.
This will calculate Response..which is Area of Active component/Area of IS component. Or Height if you have Height as Y Value in processing method. Save all changes and process a sample set. The result set will generate all results and you will use the average of all the standards and this will calculate the Response in batch divided by average Response across all the standards, is that what you are looking for?
This way you could avoid custom fields and you can repeat this label structure for multiple sets of standards/samples by assigning unique labels such as S01 or U01 etc.
However keep in mind that if you want the calculation done this way, the Dilution, Sampleweight and component editor Value must all be set at 1.00 since Amount multiplies the area ratio by Value then by Dilution and divides by Sampleweight so if you need these values for something else you need to use custom fields instead.
EmpowersBane wrote:
There is another way to do this without custom fields. Keep the labels for the standards as S1,S2 and S3 and your unknowns U1,U2..etc. Then set up lines in your sample set after your batch samples: Clear Calibration, Calibrate with a Label Reference of S* and Quantitate with a Label Reference of U*. Then in your processing method, for the component in which you want an internal standard, pick the component from the drop down column called Internal Standard.
This will calculate Response..which is Area of Active component/Area of IS component. Or Height if you have Height as Y Value in processing method. Save all changes and process a sample set. The result set will generate all results and you will use the average of all the standards and this will calculate the Response in batch divided by average Response across all the standards, is that what you are looking for?
This way you could avoid custom fields and you can repeat this label structure for multiple sets of standards/samples by assigning unique labels such as S01 or U01 etc.
However keep in mind that if you want the calculation done this way, the Dilution, Sampleweight and component editor Value must all be set at 1.00 since Amount multiplies the area ratio by Value then by Dilution and divides by Sampleweight so if you need these values for something else you need to use custom fields instead.


Well it works perfectly, awesome !
I didn't think of putting 1 in the components editor.
Everything else was correctly setup except the 1... !

Thanks to you two !

Maxime.
...not having read all of the above, I usually do this by setting up the one component as the internal standard in the processing method, then changing "Area" to "Response" in the report method. That gives you a ratio of peak of interest/IS peak (times the entered value of IS, which is frequently left at the default of 1). Make sure your response fields display enough decimal places in the report method.
Aside from these changes, treat it as you would any external standard report.
Thanks,
DR
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