pete_manc_UK said:The useful checklist is about verifiability rather than presentation.
I disagree that testing history is decisive. It tells you what a supplier did when they were being watched. Continuity of behaviour under stress — a late shipment, a failed test, a complaint — is more predictive than any run of good results.
COA_Karl said:Eight months with one supplier, then a change in how they communicate that I noticed before I noticed anything about the product.
Shipping damage protocol for vendor vetting orders: if your package arrives with visible damage, temperature excursion, or broken vials:
Reputable vendors will replace damaged shipments without argument. If they push back, that's a red flag about the vendor.
sarah.morrison said:I disagree that testing history is decisive.
Coming at sarah.morrison’s question from a different direction. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.
If somebody has the primary source to hand I would rather cite it than paraphrase it.
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsFollowing on from NurseLeah_Nash — and this may be the naive question:
How people are distinguishing a supplier having a bad batch from a supplier on the way out?
Closing the loop on my own question.
Went back through my own correspondence with an earlier supplier and the warning signs were all there in the replies, weeks before the quality changed. I was reading the product and not the behaviour.