the working standard was used as a reference standard of other working standards, yet stability of the reference working standard is not been done to determine stability potency of the standard
Reference and Working Standard Stability
If it is unstable, ‘Why are you using it as a reference standard’? Reference standards must be identified and qualified beforehand (typically UV, FTIR, NMR, MS…).
Thus, it is common to perform a ‘stability of solutions (sample, standard, mobile phase)’ in analytical method validation.
If you cannot prove through validation that your API (drug product) is stable in a ‘simple’ solvent how can you prove it meets the ICH stability requirements?
Remember, you only have ‘ONE’ chance to get a compliance © letter and thus marketing authorization. The alternative is getting a non-compliance (NC) letter and ‘verbally’ told (unless you are Pfizer, GSK, or Merck) don’t call us we will call you by the regulator!
Politicians, also are always inclined to reduce the size of the ‘under utilized regulatory force’ as they cost the taxpayer money.