If it is a product the method should be stability indicating. If it
is a raw material there is no need for it to be stability indicating
but this would be desirable. In this case you can use the
Pharmacopoeial method. In such cases I would advise against using
HPLC or other comparative instrumental techniques. Titrimetric etc
methods are primary techniques directly correlating to the chemistry
that is going on.
So in the odd scenario (exaggerating to make the point) if you test a
90% potency standard against a 90% potency sample the instrument
techniques will tell you you have a 100% potency sample. This can
never happen with primary techniques such as titrimitry, gravimetric
analysis etc etc
Rgds
J
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