How to read a Certificate of Analysis.
The COA is the single most important document in research peptide sourcing. Here is how to read one in under five minutes.
What a COA is
A Certificate of Analysis is a lab report tied to one specific manufacturing batch of one product. It documents what the material is, how pure it is, and which analytical methods were used to verify both. A supplier claim says "trust us." A COA says "check for yourself." For a deeper, section-by-section walkthrough, see our guide on how to read a peptide Certificate of Analysis.
The five things to check
1. Compound identity
The certificate should name the exact compound and its expected molecular mass. Mass spectrometry confirms the molecule in the vial matches that mass, and tandem measurements can go further and read the residue order. If the measured mass is wrong, nothing else on the document matters.
2. Purity percentage and method
Purity is typically measured by HPLC, which separates a sample into its components and reports what fraction is the target compound. Research-grade synthetic peptides are commonly specified at 95 percent or higher. Be wary of certificates that state a number without naming the method — a purity percentage is a property of the method that produced it, so two figures are comparable only when both methods are stated.
3. Batch or lot number
The lot number on the COA must match the lot number printed on your vial. A COA without a lot number, or one that never changes across orders, is a marketing document, not an analysis.
4. The testing lab
Independent third-party testing means the lab has no stake in the result. In-house numbers are not worthless, but they are not verification — and the published surveys explain why independent testing changes what a purity figure is worth.
5. The date
Analysis should be recent and should correspond to the batch being sold today, not a batch from years ago.
Red flags
- No COA available, or one produced only after repeated requests.
- Purity claimed as "99%+" everywhere, on every product, with no documents.
- Lot numbers that do not match between certificate and vial.
- Certificates with no lab name, no method, or no date.
How Steadfast handles it
Every Steadfast batch is verified by independent labs using HPLC and mass spectrometry, and a batch-matched COA is available for every product. See the certificate on each product page, or request any lot from us any time.
From the Research Blog
- What Is Peptide Purity and Why Does It Matter?
- What Is HPLC and How Does It Test Peptide Purity?
- How to Spot a Fake or Altered Peptide COA