If there is no any reference standard (IP,BP,USP) available in market for your product that time which standard is used as reference standard for the assay by HPLC test.???
Then you will have to have an organic chemist manufacture it and have it identified and characterized (MS, NMR, UV, IR…). That’s what what we did.
If the standard procure from the vendor and prepare our working standard against vendor standard. it is regulatory accepted.???
No! There is no proof that the vendor validated the method as required by ICH Q2(r1) or that you have an appropriate technology transfer report.
In this case refer WHO guideline
’Annex 3 - General guidelines for the establishment, maintenance and distribution of chemical reference substances’