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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