Chromatography Forum

Hi all,

I would like to know how to properly use the Relative Response Factors (RRF) calculated in the following reference (https://analyticalsciencejournals.onlin ... .201500106)

In my case, yield of reactions are calculated using the following formula:


If the product X is the same as the substrate S, no response factor are needed. However if X is another molecule the RRF should be used to correct the yield. This is done as follow:



RRF(IS) does notappear since it would cancel out.
When using it in this manner, I am a bit surprised that when the analyte X is basically double the molar mass of S, the term RFF(s)/RFF(x) is roughly equal to 1.1. I would have expected it to be a larger correction.

Thank you!

What units do you use for RRF?

Assuming we're talking about UV detection, molar mass has nothing to do with absorbtivity. If it did, would you really need to calculate rrf empirically?

Also, it appears that your equations are incorporating the X/IS term too many times. Internal standard area should be used to divide through your standard and analyte peak areas just once, then you treat the resulting ratios as if they were areas for use in external standard calculations... but that's a different issue.

Sorry forgot to mention that the detector is a FID used after a GC...

Does the X/IS appears too many times? Let me give you an example:

No RRF was used in this example. The yield of S does not need any RRF anyway since they would cancel out. The ration area S/ area IS would be the same as long as the substrate S is not consumed by the reaction. The difference in area of the IS at t=0 and t=1 is due to sampling different volume of the reaction.

To a close approximation for ordinary organic volatiles, an FID is a carbon counter and so it responds per unit mass not per mole.

I see... then the RRF should indeed be close to 1.

Thank you for your help!

I see... then the RRF should indeed be close to 1.

Thank you for your help!

Yes, an FID is very unselective.