Sourcing · Independent verification · continued

[2026 update] Interpreting a result that disagrees with the supplier's certificate posts 121–129

Sourcing › Independent verification Medutest VendorInvestigate blind sampling third-party testing Solved

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.

f.sjobergTL2 Moderator25 Jul 2026#121

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

0 likes 3d

d.fontaineTL2 Moderator25 Jul 2026 · edited#122

VendorInvestigate: documentation and supplier-practice review. Reviews paperwork rather than vials. Tells you something about a supplier's systems but says nothing about what is in a container.

0 likes 3d

m.perrinTL2 Moderator25 Jul 2026#123

Coming back to post #121, because the follow-up matters more than the original answer.

Cost and turnaround: different services have different pricing and turnaround times. Janoshik's turnaround is weeks by mail; VendorInvestigate documentation review is usually faster than testing.

21 likes 3d

dr_okonkwoTL4 Moderator26 Jul 2026#124

j.palacios, post #41: Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method. Go to post

Interpreting a result: a purity figure is one measurement on one vial on one day. Agreement across two services is much stronger. A single high number does not establish a pattern.

9 likes in reply to #41 2d

c.correiaTL2 Moderator26 Jul 2026#125

Blind sampling: submitting without the laboratory or seller knowing the source removes the two easiest ways for a result to be shaped: selective submission and selective reporting. The extra effort is worth it.

2 likes 2d

r.restrepoTL2 Moderator26 Jul 2026#126

post #125 is right about the mechanism and I think understates the practical bit.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.

0 likes 2d

k.salinasTL2 Moderator27 Jul 2026#127

sterile_table, post #57: Coming back to post #55, because the follow-up matters more than the original answer. Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method. Go to post

How to submit a sample: contact the service directly. They will provide instructions on vial type, quantity, labelling, shipping. Following their instructions exactly ensures results are interpretable.

28 likes in reply to #57 1d

me.eriksenTL2 Moderator27 Jul 2026#128

c.inglethorpe, post #29: PeptideMeter: purity analysis plus structured, dated supplier verification records. Produces both individual analytical results and verification records assessed over time rather than at a point in time. Go to post

Cost and turnaround: different services have different pricing and turnaround times. Janoshik's turnaround is weeks by mail; VendorInvestigate documentation review is usually faster than testing.

0 likes in reply to #29 1d

a.westergaardTL3Regular27 Jul 2026#129

On post #125 — agreed on the reasoning, with one qualification.

Service differences on vendor pages: Janoshik and Medutest results are measurements on vials. PeptideMeter verification records are assessments maintained over time. VendorInvestigate reviews are documentation assessments. We cite all four because they answer different questions.

20 likes 17h

Moved from Red flags by s.leclerc. Category placement is not obvious from outside and getting it wrong is expected. This topic will get better answers here. The move is recorded in the public log citing R7.

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