How to read a peptide COA: a 6-step check
Checked October 26, 2026.
Short answer: a Certificate of Analysis (COA) shows that a lab tested a sample. It only helps you if you can tie it to your batch and confirm it came from the lab. These six checks take about five minutes.
1. Match the batch number
The batch or lot number on the report should match the number on your package or product page. A COA for a different batch tells you nothing about what you hold. Growth Guys says the COA for each batch is on the product page and in its COA Library.
2. Confirm the lab is independent
A lab with no stake in the result is worth more than a seller testing its own product. Look for the lab's name, address and branding on the report, then search for the lab independently.
3. Verify the report on the lab's own page
Many labs, including Janoshik, host a public verification page where you enter the report's key or number. A report that exists only as a PDF on the seller's site requires nobody else to agree with it. A report you can look up on the lab's site does.
4. Read purity and identity separately
Purity says how much of the sample is the main compound, usually from HPLC. Identity says the main compound is the right one, usually from mass spectrometry. A high purity number for the wrong molecule is useless, so look for both.
5. Check the date and sample details
A COA does not spoil, but an old one tied to a batch you are not buying is irrelevant. Check the test date, the compound name, and the stated quantity.
6. Look at the whole record
A vendor that publishes only perfect numbers might be filtering. A fuller record, including lower results, is easier to trust. Compare a few reports for the same product across batches.
What a COA cannot tell you
- Whether your individual vial matches the batch. Only testing your own sample does that.
- Sterility or endotoxin levels, unless those tests are listed. They are separate tests from purity.
- Anything about safety or effects. Products here are for research use only.
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Common questions
What is a COA?
A Certificate of Analysis is a lab report showing the results of tests such as purity and identity on a specific sample or batch.
What is the difference between HPLC and mass spec?
HPLC is typically used to measure purity, how much of the sample is the main compound. Mass spectrometry is typically used to confirm identity, that the compound is what it claims to be.
Does a COA prove my vial is good?
No. It describes the batch that was tested. You need to match the batch number, and only testing your own sample verifies your vial.