Guides

Peptide COA guides

Plain-English guides to reading and verifying peptide Certificates of Analysis. Start with the basics, then move on to spotting fakes and judging vendors.

Start here

• How to read a peptide COA

  Every section of a COA, line by line, with a worked example.

• Peptide COA vs certificate of purity

  Why a purity-only document doesn't prove identity, and what to ask for.

Verify a COA or a vendor

• How to tell if a peptide COA is fake

  Seven checks, from batch matching to confirming the report with the lab.

• COA red flags

  Twelve warning signs of an edited, recycled or weak COA.

• Is a peptide vendor legit? A COA checklist

  A 15-point checklist to score a vendor's testing evidence.

• Third-party peptide testing labs explained

  What independent testing means, what labs measure, and how to judge a lab.

Understand the numbers

• What is a good HPLC purity for peptides?

  Benchmarks for 95%, 98%, 99% and "100%", and what changes the number.

• HPLC purity explained

  How reversed-phase HPLC works and how to read a chromatogram.

• Mass spectrometry explained

  Average vs monoisotopic mass, m/z charge states, adducts and tolerance.

• Peptide molecular weight table

  Reference masses and formulas for 28 compounds.

How this site works

• Methodology: how we check a COA

  Every rule and threshold the checker uses, with sources.

• About PeptideCOACheck

  Who runs the site, how it's funded, and our editorial policy.