A Certificate of Analysis (CoA) is the single most useful document a peptide supplier can give you — but only if you know how to read it. A purity percentage on its own tells you almost nothing about how that number was produced. This guide breaks down what each section of a proper CoA actually means, so you can judge whether a batch meets the standard your research needs.
Research Use Only: This guide is intended strictly for laboratory research purposes. Nothing in this article should be interpreted as medical, dosing, or usage advice.
What a Certificate of Analysis Actually Confirms
A CoA is a lab report generated for a specific manufacturing batch, confirming what that batch actually contains — as opposed to what the label claims. A genuine CoA is tied to a batch or lot number, dated, and produced by a named testing lab, ideally one independent of the manufacturer.
HPLC Purity: The Headline Number
High-Performance Liquid Chromatography (HPLC) separates a sample into its component compounds and measures the proportion made up by the target peptide. This is where the “98% purity” style figure comes from. It’s a genuinely useful number, but it only tells you what fraction of the sample is the intended compound — it doesn’t confirm that compound is the correct one. That’s what mass spectrometry is for.
Mass Spectrometry: Confirming the Right Molecule
Mass spectrometry (MS) measures the molecular weight of the sample and compares it against the expected weight for the correct peptide sequence. A CoA that includes an MS result alongside HPLC purity is confirming two different things: how pure the sample is, and that it’s actually the compound it claims to be. A CoA with HPLC data but no MS confirmation is missing half the picture.
Batch and Lot Numbers
The batch or lot number on the CoA should match the number printed on the vial or its packaging. If it doesn’t — or if the supplier can’t explain why — the certificate isn’t actually telling you anything about the product you received. Generic CoAs that aren’t tied to a specific batch are a common shortcut and worth treating with caution.
Test Date and Lab Details
Check when the testing was carried out and, where possible, who carried it out. A CoA that’s several years old, or that doesn’t name the testing lab, provides much weaker assurance than a recent, attributable report.
Reading a CoA: A Quick Checklist
- Batch/lot number matches the vial you received
- HPLC purity percentage is clearly stated
- Mass spectrometry confirms the correct molecular weight
- Testing lab is named and appears independent of the manufacturer
- Test date is recent and clearly visible
Every product in the Pyrox Labs catalogue ships with independent, batch-specific testing data. You can view current Certificates of Analysis on our Certificates of Analysis page.
