What a COA is
A certificate of analysis (COA) is a document issued for a specific production lot that reports the results of analytical tests run on that lot. It is the primary record connecting a vial on your bench to measured data. A COA is not a guarantee of quality by itself; its value depends on who ran the tests, what methods were used, and whether the data can be tied to the lot you actually hold.
Core fields to check
| Field | What to look for |
|---|---|
| Product name & sequence/CAS | Matches the compound you ordered, including salt form where stated. |
| Lot / batch number | Must match the number printed on the vial label. A COA with no lot number cannot be tied to any material. |
| Test date | Recent relative to manufacture. Old or undated reports are a warning sign. |
| Testing laboratory | Named lab with contact details. Independent third-party testing carries more weight than a self-issued report. |
| Client / submitter name | The company you are buying from should appear as the client on the lab report. If it does not, the report may belong to someone else's material. |
| Methods | HPLC (purity), mass spectrometry (identity), plus any endotoxin, sterility or heavy-metal assays. |
| Specification vs. result | Each test lists an acceptance criterion and the measured value. |
HPLC purity
High-performance liquid chromatography separates the components of a sample and reports the main peak as a percentage of total peak area. A result such as "99.2%" means the target peptide accounts for 99.2% of the detected area at the stated wavelength. Check that the chromatogram is included, not just a number, and that the method (column, gradient, wavelength) is stated. See our companion article on HPLC purity for detail.
Mass spectrometry identity
Purity says how much of the sample is one compound; mass spectrometry says which compound. The observed molecular mass should agree with the theoretical mass for the sequence within the instrument's tolerance. A COA that reports purity but no identity confirmation leaves a gap.
Net peptide content vs. purity
Lyophilized peptides contain counter-ions (often acetate or trifluoroacetate) and residual water. Net peptide content describes how much of the powder mass is peptide, while HPLC purity describes how much of the peptide-related signal is the target. They are different numbers and both matter when you calculate quantities. When labeled amounts are verified by testing, the COA should say so.
Safety and quality assays
- Endotoxin (LAL): reported in EU/mL or EU/mg against a stated limit. See endotoxin testing.
- Sterility: pass/fail. The classic method is culture in growth media for about 14 days; faster nucleic-acid (RNA/DNA-based) methods return results in hours. The COA should state which method was used, and the two are not interchangeable without validation.
- Heavy metals: typically ICP-MS results for elements such as lead, arsenic, cadmium and mercury against stated limits.
Red flags
- The seller's name is not on the report. A genuine lab report names the client who submitted the sample. If the company selling you the product is not the company on the COA, the report may have been copied from another supplier's lot and cannot be tied to the material you are buying.
- No lot number, or a lot number that does not match the vial.
- Round-number results with no chromatogram or spectrum attached.
- No laboratory name, or a lab that cannot be contacted.
- Identical COA images reused across different products or lots.
- Purity claimed with no identity confirmation.
Our approach
Every lot we release is quarantined on arrival and tested before it is made available. Documentation for a given lot can be requested at [email protected]. For our full testing program, see the Quality page.