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Peptide COA Checker
Copy the numbers from a peptide Certificate of Analysis and get an instant, plain-English verdict. The checker compares the mass-spec result to the compound's true molecular weight, checks HPLC purity, test date, batch and lab, and runs a red-flag checklist.
- RefReference masses for 28 research compounds, checked against PubChem
- m/zRecognizes m/z charge states, adducts and oxidation
- LocalRuns 100% in your browser, so nothing is uploaded
Your verdict appears here
What the checker looks at
- Identity: MS mass vs. the theoretical average and monoisotopic weight, including m/z charge states, common adducts, oxidation and look-alike compounds
- Purity: HPLC result vs. the 98% research-grade benchmark, plus claim-vs-measured gaps
- Freshness: report date older than 12 months, or dated in the future
- Traceability: named lab, who ran the test, batch/lot number, verifiable report ID
- Extras: endotoxin, heavy metals, labeled vs. measured amount
- Red flags: your checklist of signs of an edited or recycled COA
Not sure what to enter? Click Passing COA or Failing COA above to see a sample result.
What this peptide COA checker looks at
Identity: mass spec
Compares the reported mass with the theoretical average and monoisotopic mass of the selected compound, with a tolerance of ±1 Da or 0.03%. It also recognizes [M+nH]n+ charge states, sodium and potassium adducts, oxidation, and masses that belong to a different peptide. How mass spec identity works
Purity: HPLC
Flags purity under 98%, impossible values, a suspicious "100%", and labels that claim more than the lab measured. What HPLC purity means
Traceability
Checks for a named lab (and whether it's independent), a batch/lot number, and a test date within the last 12 months. See red flags
How to use it
- Open the COA PDF or image from the supplier, and make sure it's for the batch you have.
- Select the compound and copy in the mass-spec value, HPLC purity, lab, date and batch number.
- Tick any red flags you notice in the document itself.
- Read each result. Anything marked Issue or Warning is worth asking the supplier about.
New to COAs? Start with How to Read a Peptide COA, or browse reference molecular weights for every compound in the checker. Worried a document isn't genuine? Read how to tell if a peptide COA is fake, score a seller with the vendor COA checklist, or see exactly how the checker decides.
Frequently asked questions
How do I check if a peptide COA is real?
Check four things: the mass spectrometry result matches the peptide's theoretical molecular weight, the HPLC purity is measured (ideally 98% or higher), the COA names an independent lab and a batch number that matches your vial, and the test date is recent. Then look for editing artifacts and verify the report ID with the lab. This checker walks you through all of it.
What HPLC purity should a peptide have?
Most reputable research-peptide suppliers target at least 98% HPLC purity. 99% or higher is excellent. Below 95% is a significant warning sign.
What mass should the mass spec show?
The reported mass should be within about ±1 Da (or about 0.03% for large peptides) of the compound's theoretical average or monoisotopic mass. ESI spectra may instead show m/z values for multiply-charged ions, which this tool recognizes automatically.
Is my COA data uploaded anywhere?
No. The checker runs entirely in your browser with JavaScript. Nothing you type is sent to a server, stored or tracked.
Does a passing result mean the peptide is safe?
No. The checker only tests whether the numbers on a COA are internally consistent and match reference values. It cannot detect a forged document that uses correct numbers, and it says nothing about safety. Products discussed here are for laboratory research only.