Standard curve calculation
I'm trying to calculate the theoretical area of my standard curve samples based on the curve I've generated and I can't get it to work.
My calculation is "Amount*B+A". When the data is processed only the last injection processed matches with the value I would expect to see. In addition, each point on the curve has triplicate injections and the theoretical area is different for each one, when it should be the same.
Can anyone help me pinpoint what I'm doing wrong? Thanks!
My calculation is "Amount*B+A". When the data is processed only the last injection processed matches with the value I would expect to see. In addition, each point on the curve has triplicate injections and the theoretical area is different for each one, when it should be the same.
Can anyone help me pinpoint what I'm doing wrong? Thanks!
0
Best Answer

If you want to try, sometimes this will force an intersample to happen for previous sample lines.
where standards are
S1
S2
S3
Sn
S%..((S%..(Amount)*Sn.3.(A))+Sn.3.(B))or
..((..(Amount)*Sn.3.(A))+Sn.3.(B))
0
Answers
I am getting values for each injection, and most are less than 1% off what they should be. It seems like it might be building the curve as it does the calculation and therefore the A and B values are changing?
One thing I tried worked, but it is not ideal. Basically, stick a quantitate line into the sample set and reprocess those injections. Of course, you end up with double the results for your standards which is certainly not ideal. I use stock wts with purity and dilution factors vs concentrations, so I did also have to change the formula to use the Value field, purity, dilution vs just the Amount field.
I wonder if this would qualify for a "bug" issue since A and B aren't updated during processing such that custom fields are properly updated.
Label the standard injections individually (ie: S1, S2, S3). Select your target label for A and B as the last standard injection. This should calculate your equation using the correct A and B values that have been determined from the last std injection.
Example
S1 First Std
S2 Second Std
S3 Last Std
Equation targeting the last standard:
Amount*S3..(B)+S3..(A)
This is exactly what is happening, Bridget.
To clarify my suggestion as it relates to your injection scheme, triplicate injections would require a specified injection from the standards: the final injection used to generate the curve....therefore,
Equation targeting the last standard, injection 3:
Amount*S3.3.(B)+S3.3.(A)
@MJS, thank you for trying out a bunch of stuff. I couldn't get it to work when I reprocessed it with a quantitate line, so I think I might be doing it in the wrong order. Either way, not ideal, it definitely seems like a bug to me.