How to apply the test requirements in related substances tests?

Answer:

This FAQ provides guidance on how to apply the test requirements and on data interpretation in the related substances test presented in an individual monograph.

The figures given in the examples below do not apply to biological and biotechnological products, oligonucleotides, products of fermentation and semi-synthetic products derived therefrom, to crude products of animal or plant origin or herbal products or excipients (see Substances for pharmaceutical use (2034)); however the principle remains valid.

As stated in chapter 2.2.46. Chromatographic separation techniques, disregard any peak due to the solvents and reagents or arising from the mobile phase or the sample matrix.

The signal-to-noise (S/N) ratio of the specified impurities is calculated on the solution used for reporting threshold / disregard limit.