Why a purity figure tells you about a sample and not a supply chain

Started 9 January 2026 · 15 replies · 104 hearts · read 2.1k times

NolCork, IE · 9 January 2026

6 months ago

A question rather than an update: Why a purity figure tells you about a sample and not a supply chain

Putting this here because I do not want to be sold anything, I want to know what is actually established.

I would like to understand the limits of this properly rather than the headline, because the headline is the part everybody already knows.

Evidence question. I would rather have an honest "we do not know" than a confident answer, and confident answers are all I have been able to find so far.

I will summarise whatever the thread concludes and add it to my notes, in case it is useful to somebody later.

TaviaPalermo, IT

Something I would flag about the wider market: a great many names have a handful of submissions, no consistent documentation and nothing verifiable at all behind them.

TamsinRedruth, UK

My approach is to ask three questions before ordering anywhere, take the answers as data, and treat a non-answer as an answer.

SaskiaThe Hague, NL

What I found is that a supplier with hundreds of independent results behind it is a genuinely different proposition from one with four, and the difference is not marketing.

5me too 5

SunilFacilitatorBirmingham, UK

Stepping in to say that the lot-number check is the only verification that is entirely yours, and it is worth repeating on every thread here.

LucasSão Paulo, BR

What Sunil described happened to me too, in a slightly different order.

Something worth knowing: the suppliers with a long published testing record are a small group. The wider market is mostly places with two or three results and nothing else.

OsipTbilisi, GE

I asked for the certificate for my specific lot rather than a representative one, and the answer to that request tells you a great deal.

SindriReykjavík, IS

What our sourcing reference pages do is say what can and cannot be verified about a supplier. That is a narrower thing than a recommendation and it is deliberately narrow.

NylaNairobi, KE

The check I would not skip is the lot number on the vial against the lot number on the document. It takes ten seconds and it is the only check that is entirely yours.

TemSouthend, UK

Nyla, thank you for that. It gives me somewhere to start from.

My honest position is that I would rather this community discussed this openly than left the question to be answered by somebody selling.

8me too 6

NazneenDhaka, BD

#10

The thing that surprised me was how much variation there is at the thin end of the market, where a name may have one result and a website.

GwionBangor, UK

#11

Something worth knowing: certificates carry different things. The ones worth having name the method and the column, not just a percentage.

Ollie OPeterhead, UK

#12

Tem said something I want to sit with for a second.

I found the questions list on the reference pages more useful than any of the prose, because it gave me something to actually do.

ShadeIbadan, NG

#13

What I would say to somebody new is to read the risk paragraph at the top of the reference pages properly before anything else on them.

SunilFacilitatorBirmingham, UK

#14

When somebody in a thread like this changes their mind in public, having actually gone and read the thing, I would like it noticed rather than passed over. It is rare and it costs something to do.

12me too 4

BramberSteyning, UK

#15

I have read this twice now. Thank you for writing it.