This is a heads-up, not a conclusion. Everything I am confident about is below; everything I am not is marked.
Six orders from the same supplier over eight months, every one independently tested, and the consistency is the part worth reporting rather than any single result.
One flattering data point from a group buy is not consistency. Consistency means separate batches, separately commissioned, over months.
What to check: Red flags, in rough order of how much they should worry you: no verifiable address, no batch numbers, prices far under market, vendor-commissioned tests only, pressure toward irreversible payment, and shipping with no temperature control.
If your experience contradicts this, say so in the thread — I would rather be corrected here than have people act on a warning that does not hold.
COA_Karl said:Six orders from the same supplier over eight months, every one independently tested, and the consistency is the part worth reporting rather than any…
No disagreement with COA_Karl. One condition attached. The useful checklist is about verifiability rather than presentation. Independent test results commissioned by buyers rather than by the seller, consistency across multiple batches over time rather than one flattering report, a physical address and a company registration that resolve, batch and lot numbers on the actual labelling, and a shipping practice that matches what the material needs. Everything a good-looking website provides is cheap to fake; none of the items above are.
COA_Karl said:Six orders from the same supplier over eight months, every one independently tested, and the consistency is the part worth reporting rather than any…
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.
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Shop Reference StandardsThis one has a reasonably settled answer, so here it is. Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion. Synthesis, testing, and cold-chain shipping have floors. A price well under the floor means something was skipped, and the two things that get skipped are testing and content.
PurityPaulOR said:The useful checklist is about verifiability rather than presentation.
Agreed, and mass spec answers a question purity does not: identity. High purity tells you one thing dominates the chromatogram, not that it is the molecule you ordered. A mass within about a dalton of expected is the identity check.