Validation, Accuracy of related substances

[Avogadrow]

Hello,
We are trying to validate an BP method of Alverin capsule related.
The amount of mixed standard of impurities for this monograph is one ml only.
the monograph stated that you have to prepare 3 solutions, one of them is sample solution (prepare from sample by weighting an amount of capsules equivalent to 0.6 gm dissolved in 100 ml methanol), the third solution is the mixed standard of impurities and they inject it directly without any dilution.
My question is, how can we do the accuracy for such method. I mean when we do spike of the impurities standard on sample, I will spike the content of the vial of the impurity standard (one ml only) on the sample and then I have to dilute this amount to 100 ml as they stated for sample preparation. this mean that the impurity standard will diluted 100 times.
If any one faced a situation like this, please share your experience.

Thanks,
Avogadrow

[Fernando]

Dear Avogadrow

That vial of 1 ml of impurities is for identification only. The only thing that you can do in my opinion is to use the Alverin to validate the impurities. (Linearity, etc). With a bit of luck the molar absortivities are similar. If not a more complicated way is to synthesise those impurities!

Best regards

Fernando

[Avogadrow]

Thank you Fernando,
I am sorry for delaying in reply, I have a problem to login in from my PC in my office until I've login from my home.
Your suggestion is very interested, as I understand, I'll inject the vial of impurities standard and calculate the response factor of these impurities and compare with the response factor of alverine standard. if the response factor or the relative response factor (RRF) is the same so I can validate the method by using Alverin standard. If not, what should I do since we do not have enough experience or resources to synthesis these impurities. My question is, why they sell such amount which is not enough for validation or even verification of the method.

[Fernando]

Hi Avogadrow

Excuse me if I am not very clear because english is a second language to me learned long ago.
I checked the BP for the impurites of Alverine and you are not going to calculate the response factors bercause no concentrations are specified. If the limits of impurity is 0,1 % you can use the API as I stated before. Yes, the qualification of the impurities is very difficult. You have to use the services of a university for sinthesizing (I am not sure of the spelling) them.

Good luck!

Fernando

[Avogadrow]

thank you so much, your English is better than me