A certificate, line by line
| Line | What it tells you | What to check |
|---|---|---|
| Product name and sequence | Which peptide was tested | It matches what you ordered, including any Ac- at the start or -NH₂ at the end |
| Batch or lot number | Which production run | It matches your vial, box and delivery note |
| Manufacture and test dates | When it was made and tested | The test comes after manufacture |
| Expiry or retest date | How long the results stand | Your batch is inside it |
| Appearance | What the material looked like | Yours looks the same |
| Molecular formula and weight | The values expected from the sequence | They fit the sequence; our peptide calculator will tell you |
| Mass spectrometry | The mass that was measured | It matches the expected mass |
| HPLC purity | The target peptide's share of the UV-absorbing material | The figure, the method and, ideally, the chromatogram |
| Net peptide content | The share of the powder that is peptide | You need it to work out real concentrations |
| Water and counter-ion | What else is in the powder | They tell you the salt form |
| Storage | The recommended condition | It matches the label |
| Laboratory and approval | Who tested and who signed | A named laboratory you can contact |
Identity: the mass
Mass spectrometry measures the mass of the molecules in the sample, and the main signal should match the mass expected from the sequence. Two things confuse people.
Charge. The instrument reports mass divided by charge. A peptide carrying one extra proton shows at its mass plus about 1; with two, at about half its mass plus 1. A good certificate says which ion it is reporting, for example [M+H]⁺.
Average or monoisotopic. Small peptides are usually reported by monoisotopic mass, larger ones by average mass. They differ a little, so compare like with like.
A correct mass proves the molecule is present. It does not tell you how pure the sample is.
Purity: the HPLC result
The main peak is the target peptide, and its share of the total peak area is the purity. Smaller peaks are mostly related peptides from the synthesis. A peak proves something is there, not what it is, which is why a sound certificate reports HPLC and mass spectrometry together. Peptide purity explained
What a certificate does not tell you
- Sterility or endotoxin, unless a result for it is printed.
- How the product has been stored since the test.
- Anything about use in people or animals. A certificate describes a batch of material. It does not make a research material fit for a body.
A CoA and a CoC are different
A certificate of analysis gives measured results for a batch. A certificate of conformity, or CoC, is a statement that a product meets a specification, without the numbers. For a peptide you want the analysis.
Signs a certificate may not be genuine
- No batch number, or one that does not match your vial.
- The same certificate for every batch or every strength.
- Dates that do not fit: a test before manufacture, or a certificate years older than the goods.
- No named laboratory, or one you cannot find.
- A measured mass that does not match the sequence.
- A purity figure with no method and no chromatogram.
- A supplier who will not send the certificate before you order.
Where to get the certificate for our batches
Ask us for the certificate of the current batch before you order; it comes with every delivery.
Related: how we test · research-grade peptides