how we calculate the RRF inanlysis part
I have answered it in my earlier post.
If the impurity standards are available then make linearity solutions of impurity and the prepare also same concentration solution of active analyte. Then draw straight line and find out linear correlation coefficient, slope, Y-intercept and residual sum of square. Then slop of substance divided by the slope of the impurity and multiply these value by impurity %standard , you will be find RRF value. Those impurities in which no authentic reference material is available and for unknown peaks, the RRF is assumed to be 1.00.