RRF

[Daryono Hadi Tjahjono]

Dear All,

I hope some one would like to share with us how to calculate relative response factor (RRF). Is RRF for related substances/degradation products different to that of assay for the same substance?
Thank you very much.

Best regards,
D.H. Tjahjono

[syx]

For impurities for which no authentic reference material is available and for unknown peaks, the RRF is assumed to be 1.00.
The calculation of RRF is most easily performed by using a photodiode array detector and the following formula:
RRF=CiRWLi/CARWLA

RWLi is the response at the wavelength of max absorbance of the impurity.
RWLA is the respones of the impurity at the analytical wavelength.
Ci and CA are the conc of the impurity and analyte, respectively, in the solution.

[k66]

A measure of the relative response of the instrument detector to an analyte compared to an internal or external standard. Relative Response Factors are determined by the analysis of standards and are used to calculate the concentrations of analytes in samples. The RRF can be calculated using the following equation:

RFF = (Ac x Cis)/(Ais x Cc)

where,
RRF = Relative response factor
Ac = Area of the target analyte
Ais = Area of the corresponding internal standard
Cis = Concentration of the corresponding internal standard
Cc = Concentration of the target analyte

[Dan]

The RRF is used to quantitate an analyte relative to the response of a different analyte. This usually occurs for an impurity (such as a related substance) when there is no reference standard for that impurity (or the reference standard is expensive or in short supply). So, you quantitate the impurity relative to another analyte such as the API for which you do have a reference standard.

See a previous in this forum for additional comments on RRF:

http://www.sepsci.com/chromforum/viewtopic.php?t=6309

Reagrds,
Dan