Hi friends,
I need to validate a HPLC method for semi-quantitative analysis of degradation impurities in a formulation. Though it is a USP method but to show the stability indicating capability i need to do specificity ( by stress testing ) , my question is to confirm the specificity of method do i need to do the stess of formulation with active ( as done for assay ) or i need to do stress testing for all the known degradation impurities ( stress of degradation compounds)?? to see the secondry dreadation ?/ and their effect on specifity ??since the guidlines are not clear on this issue, i need your views on this .

You only need to stress the formulation with active. A placebo blank for each of the srtess conditions is also a good idea. Generally the stress conditions are limited as necessary to generate only 10%-20% degradation. This is done to minimize the amount of secondary degradation. Good luck.

Tom is correct. Make sure you also stress the drug substance alone. Sometimes the placebo can have an effect on the solution phase degradation that will not be predictive of long term stability and therefore drug substance alone should be stressed also. Also a safety note. These stress conditions can be dangerous so you should take due caution especially if the original dilution is with organic.