процентное отношение площадей пиков
https://watermark.silverchair.com/44-4-200.pdf?token=AQECAHi...
The peak areas for all impurity peaks and the peak area of the
1% reference peak for the drug were determined by integration. The known impurity percent (w/w) was determined by the
known components in the sample or by following the equation:
(1/F) • Ai /(Ar + ΣAi /100) = % impurity (w/w) Eq. 1
where F was the response factor of the identified component
(F = 1.0 for unknown components for percent A/A. The parent
drug had a response factor of 1.0;

The largest unknown impurity at retention time 35
min (RRT 1.3) is approximately 0.4% (A/A).
https://ru.wikipedia.org/wiki/Фактор_отклика