Chromatography Forum

Hello,
I just registered on this forum, and already come with a question.
I obtained at the method validation an response factor for an impurity.
When I have to write the calculation formula for that impurity I have to divided or multiply with correction factor?
Thank you very much.

Could be done either way, depending how the rrf was defined and used.

Usually, you divide by the rrf. Think about it: if the impurity respond less than the main compound, then you want to increase it.

Thank you for the answer.
See if I understand:

If the response factor is greater than unity then the corresponding area will be multiplied by a correction factor (eg 1.05).
If the response factor is less than unity then the corresponding area is divided by the correction factor (eg 0.95).
Well, the pharmacopoeia says that the response factor values ​​between 0.95 and 1.05 is considered 1.0.

it is, right?

No, you would always do it the same way.

Visualize the situation where the impurity has a higher response than the analyte. That means that the area of the impurity peak will be greater than it should be. The rrf in that case will be > 1, so you divide the area of the impurity by the rrf to bring it down to where it should be.

Now, visualize what happens when the impurity responds less than the parent,so that the rrf is < 1. In that case, you want to increase the impurity peak, so again you divide by the rrf.

Well, as Tom just said, it could be calculated either way (multiply or divide). If you are following pharmacopoeia, they usually would tell you to multiply or divide by (RRF).

If you have to calculate your own RRF, then it's a matter of which way you are getting your ratio. - (i.e analyte response over reference response, or, reference response over analyte response)

Now is logic and I understand.
Thank you very much for your time.