Assay calculation

[alaachem]

How can I calculate the assay using the calibration curve, and I have the concentration of the sample. I need the equation

[Don_Hilton]

If your calibration is a straight line through some data points, the equation has the form y=mx+b, where m and b are the result of fitting the data points to a line. The sample concentration is computed using the response from the instrument and the equation. Not knowing any more detail about what you are doing, that's about as much detail as I can give in an answer.

[rb6banjo]

Software like Microsoft Excel will do the calculations for you. As Don said, you need to make some standards of different and known concentrations and run them using your method. Once you know the instrument response (R) for your analyte you can plot the known concentration (C) vs. the response according to:

R = mC + b

Then you can use m and b (the regression terms you get from Excel) to calculate unknown concentrations using:

C = (R - b)/m

Personally, I don't like allowing for the b term. At zero concentration, you should have zero response - certainly no bigger than the integrated noise in the baseline. m and b are not independent in the linear least-squares calculations so allowing for b, skews m but this is another topic. Suffice it to say that if your analytical method is good (substantially free from interferences) and your data is a good fit to the model, b should be small.

Good luck!

[Don_Hilton]

I will add one other thing - you've told us nothing about the assay. Given the narure of this site, most of us talk in terms of what is common in chromatographic systems and with chromatographic detectors. If your assay measure percent light transmitted through a sample, then the curve will have a very different nature - and requries a logrithmic transformation to obtain a straight line.

[Peter Apps]

How can I calculate the assay using the calibration curve, and I have the concentration of the sample. I need the equation

If you know the concentration of the sample, why do you need to use the calibration ?

Peter