Dr.GutHealth said:Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion.
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.
Adding the numbers, since they settle part of this. The four things to check on any report, in order: does it name your batch, who commissioned it, what method was used, and does it report content as well as purity. A report failing any of those is weak evidence regardless of the percentage on it.
Worth separating that from certificates of analysis, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.
Dr.SurgeonPGH said:I disagree that testing history is decisive.
Coming at Dr.SurgeonPGH’s question from a different direction. The provenance questions are more useful than the numbers. Does the report name the batch on your vial. Is the date consistent with when that batch existed. Is it addressed to the vendor or to the person who paid for the test. Was the sample taken from general stock or supplied by the vendor. A perfect certificate for a different batch is worth nothing, and vendor-supplied samples are the most common way a genuine report ends up misleading.
Happy to go further on any of that.
Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsFollowing on from jim_asheville — and this may be the naive question:
How people are distinguishing a supplier having a bad batch from a supplier on the way out?
Reporting back.
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.