API or excipient specification by drug product manufacturer

Dear colleagues,
in setting the specs of API or excipients in the CoA of the drug product manufacturer, majority of tests are according Ph.Eur. curr.ed., but what if specific tests of previous editions of the same pharmacopoea are deemed important from the lab.? How should they be presented? Is in house acceptable as reference? What about validation requirement in this case?

Thank you all,