Guide · Quality
How to read a peptide COA
Peptika Redaktion · Published
Short answer: a certificate of analysis (COA) is the lab report for one batch of a peptide. A useful COA names the testing lab, the batch number on your vial, the purity measured by HPLC, the identity confirmed by mass spectrometry and, ideally, the content per vial. It is only worth something if you can check it with the lab that issued it.
What a COA should show
| Field | What it tells you | What to look for |
|---|---|---|
| Laboratory | who ran the test | an independent lab, not the seller, with a way to verify the report |
| Batch / lot number | which production run was tested | the same number as on your vial label |
| Test date | when the batch was tested | a date that fits the batch, not years old |
| Purity (HPLC) | share of the target peptide among everything the detector sees | typically ≥ 98–99 % for research peptides |
| Identity (MS) | whether the molecule has the expected mass | measured mass matches the theoretical mass |
| Content | how many milligrams are actually in the vial | close to the label claim (for example 10 mg) |
| Chromatogram | the raw HPLC curve | one dominant peak, few small side peaks |
Purity: HPLC
High-performance liquid chromatography (HPLC) separates the components of a sample. The detector records each component as a peak; purity is the area of the main peak as a share of all peaks. A result of 99 % means that 99 % of the detected signal belongs to the target peptide. HPLC does not prove which molecule the main peak is: a wrong peptide can also be "99 % pure". That is why identity is tested separately. More detail (German): HPLC explained.
Identity: LC-MS
Liquid chromatography coupled with mass spectrometry (LC-MS) measures the molecular mass. If the measured mass matches the theoretical mass of the peptide, for example about 4,731 Da for retatrutide or about 1,419 Da for BPC-157, the identity is confirmed. Small deviations within the accuracy of the instrument are normal. More detail (German): LC-MS explained.
Content per vial
Purity and content are different things. A vial can contain a 99 % pure peptide but only 7 mg instead of the 10 mg on the label. Good COAs report the measured quantity, so you can compare it with the label. Lyophilised peptides also contain residual water and counter-ions (often acetate or TFA), which is why the net peptide content is lower than the gross weight of the powder.
Additional tests
- Endotoxins: bacterial residues measured by LAL test, relevant for cell culture work.
- Heavy metals: lead, cadmium, mercury and arsenic.
- Sterility: relevant for solutions, less so for lyophilised powder.
How to tell whether a COA is genuine
- Match the batch number. The lot number on the COA must be the one printed on your vial.
- Verify with the lab. Independent labs such as Janoshik Analytical give each report a verification link or code. Open it on the lab's own website, not through a link in a PDF.
- Check the details. Is the peptide name, the amount and the test date plausible? Does the measured mass fit the substance?
- Be wary of generic reports. A COA without a batch number, without a lab name, or with the same result for every batch is worth little.
Lab reports at Peptika
Every Peptika product has its lab report on the product page. All reports are listed in the batch register with the batch number, the HPLC purity, the tests carried out and a link to the original report at the lab; with the batch lookup you can enter the lot number from your vial (both pages in German). Peptika sells its peptides as reference material for laboratory research.
Frequently asked questions
What is a peptide COA?
A certificate of analysis: the lab report for one batch of a peptide, usually with HPLC purity, mass spectrometry identity and, ideally, the measured content per vial.
What purity should a research peptide have?
Research peptides are usually offered at 98–99 % purity or more, measured by HPLC. Purity alone does not prove identity; that needs mass spectrometry.
What is the difference between HPLC and LC-MS?
HPLC measures purity: how much of the sample is the main component. LC-MS measures the molecular mass and so confirms that the main component is the right peptide.
How do I verify a COA?
Compare the batch number with your vial and open the report on the testing lab's own website using its verification code or link.
Where can I see Peptika's lab reports?
On every product page and in the batch register, with links to the original reports at the lab.