A certificate of analysis (COA) is the document that ties a vial to laboratory test results. For research peptides it is the single most useful piece of paperwork you can ask for, and it only takes a few minutes to read one properly. This guide walks through each part of a typical peptide COA and what to look for.
What a COA is (and isn’t)
A COA reports the results of specific tests performed on a specific batch, usually called a lot. It tells you what the lab measured, how it measured it, and what it found. It does not certify a product for any particular use, and a COA for one lot says nothing about a different lot. That is why the lot number is the first thing to check.
The sections of a typical peptide COA
1. Product and lot identification
The header should name the compound, the stated amount per vial (for example 10 mg), the lot or batch number, and the test date. The lot number on the COA should match the lot number printed on the vial label. If it does not match, the report does not describe the vial in your hand.
2. Identity: mass spectrometry (MS)
Mass spectrometry confirms that the material is the compound it claims to be. The report usually lists an expected (theoretical) molecular mass and the observed mass. These should agree closely. Many labs include the spectrum itself, showing the main peak at or near the expected mass.
3. Purity: HPLC
High-performance liquid chromatography (HPLC) separates the components of a sample. Purity is reported as the percentage of the total signal that comes from the main peak. A clean chromatogram shows one dominant peak with only small peaks around it. The report should state the purity figure and ideally include the chromatogram image.
4. Quantity or content (when tested)
Purity and quantity are different measurements. A sample can be high purity but contain less material than the label states. Some COAs include a net peptide content or a quantitative assay that measures how much compound is actually in the vial. When it is present, compare it with the stated fill amount.
5. Laboratory details and signature
A credible report names the testing laboratory, includes a report or sample ID, and is signed or otherwise authenticated. Independent third-party labs are generally preferred over in-house testing because the lab has no stake in the result.
A quick checklist for every COA
- The compound name and stated amount match what you ordered.
- The lot number matches the vial label.
- The test date is recent enough to be relevant to the lot.
- Identity (MS) and purity (HPLC) results are both reported, with methods named.
- The testing lab is named and the report has an ID you could reference.
Red flags
- No lot number, or one that does not match the label.
- A purity number with no chromatogram, method or lab name behind it.
- The same report reused across different products or many lots.
- Images that look edited, cropped to hide details, or inconsistent fonts and dates.
How 406 Peptides handles COAs
We post certificates of analysis to our COA library by product and lot as laboratories provide them. If a lot is still pending, the library says so. You can also request a COA for a specific product and we will email it to you when it is available.
All 406 Peptides products are sold for laboratory research use only. They are not for human or veterinary use, and nothing in this article is medical advice.