What Every Test on a Peptide COA Actually Measures (And Why It Matters)
By RUOcodes.com Research Team
Published: · Updated: Sep 6, 2026
Every test on a peptide COA explained: HPLC purity, mass spec identity, LAL endotoxin, sterility, and what a failing result actually means.
For research and education only. Not medical advice. Direct Answer A peptide Certificate of Analysis (COA) is only trustworthy if it comes from an independent third-party lab and includes three core tests: HPLC purity (look for 98%+, ideally 99%+), mass spectrometry to confirm molecular identity, and net content to confirm actual quantity. An in-house COA from the vendor itself does not count as verification. 98%+ HPLC purity is the baseline credible threshold; 99%+ signals a quality-focused vendor 3 core tests every credible COA must include: HPLC purity, mass spectrometry, net content Independent third-party testing — not vendor in-house testing — is the standard the research community holds vendors to What Each COA Test Actually Measures Test What It Measures What It Tells You HPLC Purity Purity percentage via high-performance liquid chromatography Whether the sample is mostly the target compound or diluted with impurities Mass Spectrometry (MS) Molecular identity Whether the compound is actually what it claims to be, not a substitute Net Content Actual quantity present in the vial Whether you're getting the labeled amount, not an underfilled vial If you have spent any time sourcing research peptides, you have seen the term COA thrown around constantly. Certificate of Analysis. Vendors advertise it. Communities demand it. And yet a surprising number of researchers glance at it, see a few numbers and the word "Pass," and move on without truly understanding what they are looking at. That is a problem, because a COA is only useful if you can read it. And in a market where vendor quality varies dramatically, knowing what each line item actually measures is one of the most important skills a serious researcher can develop. This guide breaks down every major test you will encounter on a peptide COA, written in plain language without the textbook jargon. No chemistry degree required. What Is a COA and Why Does It Exist? A Certificate of Analysis is a document from a lab…
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