I would like to get clarification regarding the nitrosamines method validation for the drug product being done. Whether for the drug product in specificity whether need to inject all the nitroso impurities likely in the 10 derivatives or only the drug product impurities shall be performed? Moreover how to consider for the limits for the unknown nitroso impurities?
For method validation you should consider only those nitrosamines for which a risk exists. It is unlikely that your product can be contaminated with 10 nitrosamine impurities!
Regarding the limit for new nitrosamine impurities, you should either consider an AI of 18 ng/day or derive an AI using a suitable surrogate with known TD50. Refer attached guidance.