Guide
How to Read a Peptide COA (Certificate of Analysis)
A Certificate of Analysis (COA) is the lab report that describes a specific batch of material. Most people glance at one number and move on. Here is how to read all of it, and the one detail that tells you whether the report actually describes your vial.
What a COA is (and is not)
A COA documents the analytical testing performed on a specific lot of material: what it is, how pure it is, and often whether it passed contamination screening. It is a record of measurement, not a marketing claim.
A COA is not a safety endorsement or a use recommendation. For research reference materials it simply describes the sample; it says nothing about human use, and reputable ones make no such claims.
Identity: mass spectrometry
Identity confirms the sample is the molecule on the label. Mass spectrometry (MS) measures the molecular weight and is the most common identity method on a peptide COA.
If a report shows a purity figure but no identity confirmation, you know how clean the sample is but not whether it is the right compound. You want both.
Purity: HPLC
Purity is usually reported by High-Performance Liquid Chromatography (HPLC) as a percentage. It reflects how much of the sample is the target compound versus impurities.
Higher purity means fewer unknown variables in downstream research. Figures in the 98–99%+ range are common for well-made reference peptides.
Endotoxin: the LAL test
Some COAs include an endotoxin result, typically from the Limulus Amebocyte Lysate (LAL) assay, reported in EU/mL. This is the test many suppliers skip.
For in-vitro work, endotoxin contamination can distort results, so a documented "pass" is a meaningful quality signal when it is present.
Batch number and test date
Near the top or bottom of a real COA you will find a lot/batch number and the date the testing was performed, along with the analytical methods used.
These make the report traceable: you can match the batch code on the report to the code on the vial, and the material can be re-verified later.
The biggest tell: per-batch vs generic
The most important thing a COA can tell you is whether it belongs to your material. A per-batch COA carries a lot number that matches the vial you received. A generic, brand-level COA describes some earlier batch and may have nothing to do with what shipped to you.
When you can enter a batch number and pull that batch’s exact report, the paperwork stops being a leap of faith.
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