[PeptideChecked]

Start with the lot number, not the purity figure

The first thing I look at on any COA is whether the lot number on the report matches the lot number on the vial, box or shipping label. A COA that shows a purity percentage but no lot number, or a lot number that does not correspond to anything you received, is decorative – it documents a test, just not a test of your material. Ask the vendor for the lot number before you order, then confirm it matches on arrival. Vendors who cannot answer that question before payment are telling you something useful.

Check whether the lab is named and reachable

A real third-party report names the laboratory that performed the analysis. From there, the useful checks are whether that lab actually exists as an independent entity, whether it publishes its own methods, and whether the report carries a verifiable report or sample ID you could reference with the lab directly. “Third-party tested” with no lab name is a marketing phrase, not documentation. If a vendor names a lab, it is worth checking whether that lab appears in any enforcement or warning-letter record – that history is public and it matters.

Look at what the report actually measures

Purity by HPLC and identity by mass spectrometry answer different questions, and a report that only shows one is only half a document. A useful COA shows the analytical method, the instrument or method reference, the measured result against a specification, and a date. Watch for reports with no date, no method, or a result that reads as a round number with no supporting chromatogram or spectrum. Also check whether the document is a scan of an original report or a vendor-designed template that merely resembles one.

Check the chain, not just the paper

A COA is only as good as the chain behind it: who commissioned the test, which batch it covers, and whether the same report is being reused across multiple products or dates. Reused reports and recycled lot numbers are one of the more common patterns, and they are easy to catch once you start comparing documents across a vendor’s catalogue. If you want a longer walkthrough of the fields to check and what each one should contain, I keep a reference here: https://peptidechecked.com/guides/how-to-read-a-peptide-coa

Over to you

For anyone who has gone through this: what is the single check that has most often caught a bad COA for you – the lot number, the lab name, or something in the analytical detail? And has anyone here successfully verified a report ID directly with a named lab?

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