Adipotide, which studies are actually worth reading?

I would want to see this replicated by a group that is not the one who published the original before I changed anything.

Not accusing anyone of anything, I just do not think a number means much until you can see what is behind it.

Batch-to-batch variation is the thing people underestimate. A passing result certifies one lot, not a product line, and vendors know most buyers do not make that distinction.

Answered your second question in a DM since it was getting long, but short version is yes with caveats.

Reversed-phase HPLC with UV detection at 214nm is the standard here because the peptide bond absorbs there. If a vendor reports purity without stating the method or wavelength, the number is not comparable to anything.

If you want to check this yourself, ask the vendor which laboratory issued the certificate, then email that laboratory with the report number. Most will confirm or deny. The ones that go quiet tell you something.