A certificate of analysis (COA) is the single most useful document a research peptide supplier can give you. It tells you what was tested, how, and what the results were for one specific batch. This guide walks through a typical peptide COA section by section, explains what each number means, and lists the warning signs that a certificate should not be trusted.
What a certificate of analysis is
A COA is a batch record. When a lot of peptide is manufactured, samples from that lot are analyzed and the results are written up against a set of specifications. If the results meet the specifications, the batch is released and the COA travels with it.
Two things follow from that definition. First, a COA belongs to one batch, not to a product in general. A COA without a batch or lot number is a brochure, not a certificate. Second, the COA is only as good as the testing behind it, so it matters who performed the analysis.
Who issues the certificate
Peptide COAs usually come from one of two places:
- The manufacturer’s own quality control (QC) laboratory. This is the most common source. The manufacturer tests each lot before release and issues the certificate.
- An independent third-party laboratory. The supplier sends a sample to an outside lab, which issues its own report under its own name.
Both are legitimate, but they are different, and a good supplier tells you which one you are looking at. At PeptiCore Labs, our certificates are issued by our manufacturer’s QC laboratory for each batch, and we label them that way.
Section 1: the header
The top of a COA identifies exactly what was tested. Look for:
| Field | What to check |
|---|---|
| Product name | Matches the product you ordered, including the amount per vial (for example 10 mg). |
| Batch / lot number | Matches the number printed on your vial label. This is the most important check on the page. |
| Manufacture date | When the lot was produced. |
| Retest date | The date by which the material should be re-evaluated. Stored correctly, freeze-dried peptides are typically given a retest window of one to two years. |
| Appearance | Usually “white to off-white lyophilized powder”. A description that does not match what is in your vial is worth querying. |
Section 2: HPLC purity
High-performance liquid chromatography (HPLC) separates the components of a sample and measures how much of the total signal belongs to the target peptide. The result is reported as a percentage, for example 99.12%.
What that number means in practice:
- It is a relative purity. It is the area of the main peak as a share of all detected peaks. Impurities are usually closely related peptide fragments or sequences missing an amino acid, left over from synthesis.
- Higher is better, but context matters. Most research-grade peptides are specified at 98% or above. The difference between 99.1% and 99.4% is rarely meaningful on its own; the difference between 99% and 92% is.
- A chromatogram is a good sign. Many COAs include the trace itself: one tall main peak and small minor peaks. A purity figure with no method, no trace and no batch number tells you very little.
For a deeper explanation of how the test works, see our upcoming guide to HPLC purity.
Section 3: identity by mass spectrometry
Purity tells you how clean the sample is. Identity tells you whether it is the right molecule. Mass spectrometry (MS) measures the molecular weight of what is in the vial and compares it with the theoretical weight of the target sequence.
On a COA you will usually see either the expected and observed mass side by side, or a mass spectrum with a statement such as “consistent with product identity”. Small differences of a fraction of a dalton are normal. A large mismatch means the material is not what the label says.
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You can compare a certificate against the expected values on our product pages. For example, the BPC-157 product page lists its sequence, molecular formula and molecular weight.
Section 4: safety and contamination tests
Some certificates go further and report:
- Bacterial endotoxin, usually by LAL assay, reported in EU per mg. Endotoxins can interfere with cell-based and other biological experiments.
- Microbial limits, such as total aerobic count and yeast and mold.
- Water content or peptide content, which affects how much actual peptide is in a vial of a given gross weight.
These are not on every COA, but when they are, they should have units and a specification, not just “pass”.
Red flags on a peptide COA
- No batch or lot number, or a batch number that does not match your vial.
- The same certificate used for several different products or sizes.
- Two different products sharing one batch number.
- Purity shown with no test method, no date and no chromatogram.
- No identity test at all, only a purity figure.
- Results that are suspiciously round (exactly 99.00%) across every product.
- A certificate that cannot be tied to the company you are buying from.
How to match your vial to its certificate
- Find the batch number on your vial label.
- Go to our COA Lookup page or open the product page.
- Open the certificate and confirm the product name, amount and batch number all match.
- If anything does not match, or a certificate is not yet posted, contact support with your order number and we will send the correct document.
Frequently asked questions
Is a manufacturer COA as good as a third-party COA?
Both can be reliable. A manufacturer’s QC certificate is the standard batch release document. An independent lab report adds an outside check. What matters most is that the certificate is batch-specific, dated, reports methods and results, and is honestly labeled as one or the other.
What HPLC purity should a research peptide have?
Most research-grade peptides are specified at 98% or higher by HPLC. Always read the purity alongside the identity result and the batch number.
Why does my COA show a retest date instead of an expiry date?
Retest dates are common for research materials. They indicate when the material should be re-evaluated, assuming it has been stored as specified.
Can I get the COA before I order?
Yes. Certificates are available on the product page or through COA Lookup. If one is not posted yet, ask our support team and we will send it.
All PeptiCore Labs products are sold for laboratory research use only and are not for human or veterinary use. Certificates of analysis document the identity and quality of a batch; they are not evidence of safety or suitability for any use in people or animals.