How we can declare the potency of any compound which doesn't have any standard. what is the maximum deviation allowed in this potency considering all the errors?If we have one standrad having the declared purity of 98.00%. on the basis of this standard we analysed another compound and found the purity of 97.20%.
The Customer require minimum 97.00% assay. now if the deviation in standred is 1-2% then my results may vary based on the Variation of Standard.
The answer to your question depends on how the company, supplying your standard, defines the standard's purity. Some companies state that the purity is "greater than" 98%, which is a statistical statement saying that the standard most likely contains less than 2% impurity, but leaves some uncertainty in the actual amount. Others state that the purity is, in fact, 98% because there is 2% of a known impurity; for example, water. If you have the latter case, you can easily compensate for the presence of the impurity.
However, there is a statistical component that applies to both of the cases. It is the question of how certain you are in the answer that your assay provides. This will depend on both the precision by which the purity of the standard is known and the precision of your assay (I think the certainty in the assay's result is the product of the certainty of the standard's purity and the precision of the assay).
If you want to be truly rigorous, you should make the purity measurement several times (at least 3) and give the 95% confidence interval for the purity.
If we doesn't have any reference material and if we prepare the purest material by column fractionation, distillation crystallization etc. and analysed it with any three methods ( Titration, GC , HPLC NMR, GC mass and LC mass)
Now please guide me is it really possible to declare the purity on the basis of the average of the purity of three techniques taking consideration of Moisture, sulphated ash and residual solvents.
Basically my question is what is the minimum requirement for declare the assay of any compound whose reference standard sample is not available in the market
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