A certificate of analysis is the closest thing this market has to a receipt for quality. It is the document that says: this batch was tested, here is what the test found, and here is who did the testing. When we write about a shop, the COA is the first thing we look for and — too often — the first thing we have to mark as “not published”. This guide walks through one the way we read it at the desk.
Start with the header, not the purity number
Most readers jump straight to the big percentage. Resist that. The header tells you whether the rest of the page deserves your trust.
- Laboratory name and address. A real, identifiable lab should be named, ideally with contact details you can check. “In-house QC” is not worthless, but it is a shop marking its own homework.
- Report or sample ID. Every legitimate report carries a unique identifier. If two different products share an ID, or the field is blank, stop there.
- Date of analysis. Note it. A report from a year and a half ago describes a batch that has probably sold out.
- Client name. The shop should appear as the client. If the client is a different company, it is fair to ask why.
Match the batch, every time
The single most important check is the simplest: the batch or lot number on the COA must match the number on the vial or the order you receive. A beautiful certificate for a different batch tells you nothing about yours.
This is why we prefer shops that publish COAs per batch rather than one “representative” certificate per product. Where a shop publishes nothing, the practical answer is to ask for the COA of your batch before you pay — our separate guide covers how to ask.
The identity result
Purity tells you how much of the sample is the main compound. Identity tells you whether the main compound is the one on the label. They are different questions, and a COA should answer both.
Identity is usually confirmed by mass spectrometry (MS). The report should state the expected molecular mass and the observed mass, and the two should agree within the tolerance the lab states. A line that just says “conforms” with no numbers is weaker evidence than one that shows its working.
The purity result
Purity is usually measured by HPLC, and expressed as a percentage of the total peak area. Look for:
- The method. HPLC, often with a UV detector. The report may list the column and wavelength; that is a good sign of a real analysis.
- The chromatogram. A picture of the peaks. One dominant peak with small neighbours is what you hope to see. A report with a percentage but no chromatogram asks you to take the number on faith.
- What “98%” means. It means 98% of what the detector saw at that wavelength was the main peak. It does not tell you about water content, salts or anything the detector cannot see.
When a shop states a purity figure — Peptid24, for instance, states at least 98% for its lyophilized peptides — the COA is where that claim is either backed up or left hanging. A stated figure on a product page is a claim; a batch COA with a chromatogram is evidence.
Net content and appearance
Some certificates also report net peptide content, appearance (“white lyophilized powder”) and solubility. These are useful, but secondary. A report can look thorough by listing many fields; the fields that carry the weight are still lab, batch, identity and purity.
Red flags we note in the ledger
- No lab name, or a lab you cannot find anywhere else.
- The same report ID on different products or batches.
- Round, identical purity numbers on every product (99.0%, 99.0%, 99.0%).
- Edited-looking text, mismatched fonts, or a date in the future.
- A COA that is only available as a low-resolution image with the batch field cropped out.
None of these proves a problem on its own. Each is a reason to ask one more question before ordering.
When a shop hasn’t published COAs
This is the common case. Among our partner shops, Nexo Research says plainly that its lab reports are not published yet, and we found no public reports for the others either. In our tables, that reads “not published” — not “no”, and not a guess.
It does not have to stop you, but it changes the order of operations: ask for the batch COA first, read it with this guide beside you, and only then use a reader code. If a shop sends a report, check it against the list above. If it does not, that is information too.
A one-minute checklist
- Is the lab named and findable?
- Does the batch number match yours?
- Is there an identity result (MS) with numbers?
- Is there a purity result (HPLC) with a chromatogram?
- Is the date recent enough to be your batch?
Five yeses do not make a perfect product. But a shop that can give you five yeses is a shop that keeps its paperwork in order — which is exactly what a ledger is for.
Products sold by these shops are for laboratory research use only. Nothing in this article is medical advice.