
 Posts: 17
 Joined: Wed May 11, 2011 8:20 am
We calculate impurities using regression equation. We don’t Just use 100% standard solution. We prepare LOQ, 100% and 120% solutions in release test and calculate using y=mx+b
Authority asked “Why do you substract intercept value from impurities area? Please show scientific source.”
Example:
Impurity content % = (Ab)/m x 100/5 x 100/L
A: Impurity area from test solution
b: intercept value from standard solutions linearity
m: slope from standard solutions linearity
100/5: dilution factor
L: Label claim
How can we response the question?
Thank you