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Quality & trust
What Is a COA (Certificate of Analysis)?
It's the single best tool for telling whether what's in the vial matches the label. If you learn to check one thing before sourcing a peptide, make it this.
A Certificate of Analysis — a COA — is a lab report tied to a specific batch of a compound. It's the single best tool you have for telling whether what's in the vial actually matches what's on the label.
Research use only. This article explains how to interpret
laboratory testing documents. It is not medical advice and does not describe human use.
What a COA actually is
For peptides, a good one documents two things above all:
- Identity — proof the compound is what it claims to be, usually via mass spectrometry (MS), which measures the molecular weight.
- Purity — how much of the sample is the intended compound versus impurities, usually via HPLC, reported as a percentage.
It should also list the testing lab, a batch/lot number, and a date — the details that let you match the certificate to the vial in your hand.
How to read HPLC purity
HPLC separates everything in the sample and measures the proportion of each component. The headline number is the purity percentage:
Reputable research peptides are commonly 98–99%+ by HPLC
On the chromatogram, one large dominant peak (the target compound) with only tiny peaks around it is what high purity looks like. You don't need to read the graph in detail — but the stated percentage should be high and reference that batch, not a generic claim.
There's a big difference between a seller saying "99% pure" and an independent lab saying it.
Why third-party testing matters
| Vendor-only claim | Third-party COA |
|---|---|
| Produced by the seller | Produced by an independent lab |
| Incentive to look good | No stake in the result |
| Hard to verify | Traceable to a named lab and batch |
Independent third-party testing is the gold standard because the lab has no reason to inflate the figure. A named lab on the certificate is a strong positive signal.
Red flags — when to walk away
- No COA at all. The biggest red flag. Pass.
- A purity claim with no document behind it. "99% pure" on a page means nothing without the report.
- No lab name, batch number, or date. An untraceable certificate isn't a certificate.
- The same COA reused for every batch. Testing is per-batch; one recycled PDF is a warning sign.
- Identity (MS) missing entirely. Purity without identity doesn't confirm the right compound.
How to verify before you buy
- Ask whether a COA is included with the order (it should be).
- Check that it names a real testing lab and a batch number.
- Confirm it shows both identity (MS) and purity (HPLC).
- Make sure the purity figure is specific and high (98–99%+).
Once you've got clean material, the next step is preparing it correctly — see How to Reconstitute Peptides.
Where to buy
A source that tests every batch
We recommend Vital Chems — they put their testing where their mouth is.
- Third-party HPLC tested — COA on every order
- Same-day shipping before 1:30 PM PT
- US-based, fast and responsive support
Frequently asked questions
What is a COA for peptides?
A Certificate of Analysis is a lab report documenting a compound's identity and purity — typically an HPLC purity percentage plus a mass-spectrometry result confirming molecular weight, along with the lab, batch number, and date.
What purity should a research peptide be?
Reputable research peptides are commonly tested at 98–99%+ purity by HPLC. The COA should state the exact figure for that specific batch, not a generic claim.
What's the difference between a vendor COA and a third-party COA?
A vendor COA is produced or commissioned by the seller; a third-party COA comes from an independent lab with no stake in the result. Independent testing is more trustworthy because the lab has no incentive to inflate the numbers.
Should a COA come with every order?
Reputable sources provide a batch-matched COA with the order. If you have to fight to get one, that tells you something.