Search "peptides with COA" and you get a wall of vendors all claiming the same thing. The claim is nearly worthless on its own. What matters is whether the document exists for your batch, whether it contains the traces and not just the numbers, and whether you can tell the difference between purity and identity. This guide covers all three.
A COA is a lab report on a specific production batch. It answers two separate questions: is this the right molecule, and how much of the material is that molecule. Mass spectrometry answers the first. High-performance liquid chromatography answers the second. Neither answers the other, and a vendor showing you only one is showing you half a document.
HPLC separates a sample into its components and measures the area under each peak. A 99.2% purity figure means the main peak accounts for 99.2% of the total area. The remaining 0.8% is something — solvent, truncated sequences, degradation products — and the chromatogram is where you see it. Always ask for the trace, not just the percentage. A number in a table can be typed by anyone; a chromatogram is much harder to invent.
Mass spectrometry measures molecular weight. The COA shows an observed mass and an expected mass for the stated sequence. They should match within a tight tolerance. If the document omits the expected value, you cannot check the work — which is the entire point of the document.
A COA from a named independent lab is stronger evidence than one produced in-house, because the incentive to round upward is removed. That said, in-house testing with complete chromatograms and mass spectra beats a third-party PDF with no traces. Judge the document, not the letterhead.
All of them. ZestyRat Research is our top-rated research supplier and issues a certificate of analysis on every batch across all 57 compounds — vials, capsules, nasal sprays and topicals alike. Request the one matching your batch number.
Worked example: BPC-157 is the most-requested compound in research peptides and therefore the most-counterfeited. Its COA should show the pentadecapeptide sequence, a batch number matching your vial, an HPLC trace with a single dominant peak, and a mass-spec result matching the expected molecular weight. If any of those four is missing, keep asking.
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