Numbers first: sampling plan · FGP.
This is a planning question. I know what my options are; I do not know how to weigh them.
What I want is the minimum viable version, which I suspect is smaller than what I would design.
What is the minimum version of this that is still defensible?
Before anything else, check that the lot number on the certificate matches the vial in your hand — that traces back to your material and not to some other lot from some other date.
Lot number visibility is the first check, and it is the one most certificates fail — the number is not printed on the vial, or it is on the certificate but the vial is unmarked.
Stated carefully, the laboratory name and accreditation status can be checked in real time against the testing service's own register, and that two-minute check catches substituted certificates.
Published inter-laboratory comparisons of the same material routinely find spreads of half a per cent to a full per cent, which sets realistic expectations.
The practical summary: check the lot number, ask for the method, and reserve judgement until you have both.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsAsk whether the certificate answers the question you are actually asking, because the answer is often no.
Writing the lot number on your vial in permanent marker is worth doing because it later proves that the certificate traces to your material.
Batch versus lot is a semantic distinction that determines whether one certificate applies to ten vials or to one, and checking this distinction is worth a minute.
My working rule is that a document without a lot number, a method section and a test date is marketing.
edited 22 Jun 2026 by kirsi_lahtinen — clarified the distinction between purity and content
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.