Does a red flag mean a COA is fake?

No. Each item is a reason to check further, and most have innocent explanations such as a template, a rounding habit or a clerical slip. Several flags together, or a laboratory that cannot confirm the report, are more concerning.

How can I tell whether a chromatogram was reused?

Compare the chromatogram images from different reports. Identical peak shapes, baseline noise and axis details across different batches, products or vendors are a strong sign the image was reused. Different batches rarely give pixel-identical traces.

What is the single best check?

Confirming the report with the issuing laboratory, using the verification key, QR code or lookup it provides. If there is no way to do that, treat the document as an unverified claim.

Signs a COA may be reused, edited or unreliable

By PeptideProof · Updated 12 October 2026 · 7 min read

Most Certificates of Analysis are what they say they are. But documents are easy to copy, edit and recycle, so it helps to know what to look for. Below are ten things worth checking, with how to follow each one up.

Read this first

A flag is a prompt to check, not proof of anything. Templates, rounding habits and typos are common and innocent. What matters is whether the laboratory itself can confirm the report. This list is about documents, not about the people who sent them.

The ten checks

1. The same chromatogram appears on different reports

Two batches, products or vendors should not share a pixel-identical chromatogram. Compare the images side by side: identical peak shapes, baseline noise and axis labels across different reports suggest reuse. Follow up: ask the laboratory for the raw data for that report.

2. The dates are out of order

A report issued before the sample was received, or analysed before it arrived, or dated in the future, is internally inconsistent. Follow up: ask the seller for the original file and check it with the laboratory.

3. The QR code points somewhere unexpected

A QR code should lead to the laboratory’s own verification page for this report. If it goes to a different domain, or to a page showing a different report number, that’s a mismatch. Follow up: open the link and compare the report number, sample and results.

4. There is no way to verify it

No report key, no QR code, no lookup — just a letterhead. A letterhead is easy to copy. Follow up: ask which laboratory issued it and contact the laboratory directly using contact details you find yourself.

5. The quantity is far from the amount declared

Gaps of a few percent are normal; a large gap in either direction deserves a question. Purity doesn’t explain it.

6. The sample is vaguely identified

“Peptide sample”, no batch number, no declared amount. Without a batch number the report can’t be tied to a product. Follow up: ask which batch was tested and compare it with the one on your vial.

7. No methods are named

Results with no method — no HPLC wavelength, no mass-spectrometry result for identity — can’t be interpreted properly.

8. The laboratory is hard to find

No website, a misspelled name, or a domain that doesn’t match the one on the report. Follow up: search for the laboratory independently rather than using links on the document.

9. The file looks edited

Mixed fonts, text that doesn’t line up, results pasted over a scan, or a PDF created by consumer software long after the stated date. File properties (producer, creation and modification dates) can tell a story. PeptideProof checks some of these automatically.

10. The report is only a screenshot, or pages are missing

A cropped image or a single page of a longer report hides what’s around it, such as differing report numbers on other pages. Follow up: ask for the complete original.

What to do about a flag

Ask the seller for the original file and the laboratory’s verification details.
Confirm the report with the laboratory itself.
Compare it with other reports from the same seller or batch.
Treat an unconfirmable document as an unverified claim, whatever it says.

For a worked example of how this shows up in a report, see the example report.
For one laboratory’s verification route, see how to verify a Janoshik report.

Frequently asked questions

Does a red flag mean a COA is fake?: No. Each item is a reason to check further, and most have innocent explanations such as a template, a rounding habit or a clerical slip. Several flags together, or a laboratory that cannot confirm the report, are more concerning.
How can I tell whether a chromatogram was reused?: Compare the chromatogram images from different reports. Identical peak shapes, baseline noise and axis details across different batches, products or vendors are a strong sign the image was reused. Different batches rarely give pixel-identical traces.
What is the single best check?: Confirming the report with the issuing laboratory, using the verification key, QR code or lookup it provides. If there is no way to do that, treat the document as an unverified claim.

See it on a real document

PeptideProof reads a COA for you and shows what is only reported, what has no evidence and what looks inconsistent. See an example first, or check your own — new accounts include free analyses.

See an example report Verify a COA

More guides

Educational information about reading laboratory documents. It is not medical, dosing or purchasing advice, and it doesn’t say that any product is safe, legal or suitable for any use. See the medical and research-use disclaimer.