Hello,
Thank you very much for the discussions, we are currently trying the recommended experiments and will get back with the results.
@elenipoliti The impurity is listed in Appendix 1 from Q&A under “other N-nitroso structures”. According to the guideline, since the impurity is listed and if it is available, the same should be included in a risk assessment and supported by confirmatory testing. Our concern was that if the reference standard in not stable, are we liberated from confirmatory analysis, since according to Q&A if the standard cannot be synthetized, that confirmatory analysis is not required.
Currently we are doubting the stability of the reference standard that is in solid state. We have obtained it from two vendors, they both had it synthetized 4-5 months before the delivery arrived. The standard may have been stable for a shorter period, but we do not have evidence that the standard is not degraded, since we cannot detect it in the samples that we have received.
We will try the experiments that are suggested in this group and in @N nitroso tadalafil and will get back.
Best regards,
Bojana