A Certificate of Analysis, or COA, is one of the most important documents in your sourcing process. It is the evidence behind a quality claim. But a COA is only as useful as your ability to read it.
Here is how to read one and what to watch for.
What a COA actually is
A COA is a lab report tied to a specific batch of a compound. It records what was tested, how it was tested, and what the results were. At minimum, a credible COA should show the compound name, the batch or lot number, the test date, and the analytical results for purity and identity.
Think of it as the compound’s paper trail. If a question comes up later about quality or a research anomaly, the COA is where you start. A vague or generic document gives you very little to work with.
Purity is the headline, not the whole story
Purity is the number most suppliers lead with. It is usually measured by HPLC, or high-performance liquid chromatography, and reported as a percentage. A 99% result means that, of what the method detected, about 99% was the intended compound.
That is useful. It is also one data point. HPLC reports what the instrument can see under the conditions of that specific test. It does not describe everything that might be in the vial. A 99% purity figure is a strong signal, but only when you also know how it was measured and what else was checked.
Mass spectrometry, or MS, confirms the molecular weight and identity of the compound. Purity tells you how much of one thing is in the vial; MS will tell you what that thing is. A COA that reports purity but never confirms MS is telling you only half the story.
Why endotoxin values are important.
Endotoxins come from bacterial cell walls. HPLC cannot detect them. Mass spectrometry cannot either.
That means a compound can show 99% purity and still carry endotoxin contamination that neither test would ever flag. In research work, that kind of contamination can throw off results in ways that are hard to trace back to their source.
Endotoxin testing uses a separate method, usually a LAL assay, short for Limulus Amebocyte Lysate, or a modern equivalent. A complete quality panel includes it. If a COA reports only purity, it is giving you an incomplete picture, no matter how high the number looks.
COA Checklist
As you’re reading your compound’s COA, you should be checking for these things…
- Does the lot number on the COA match the vial you received?
- Is purity reported with a method, usually HPLC, and an actual chromatogram, not just a number?
- Is the compound’s identity confirmed, usually by mass spectrometry?
- Is there endotoxin testing, and not purity alone?
- Was any of the testing done by an independent third party?
- Is the test date recent and tied to this batch?
Looking for a new peptide supplier?
PEARL is built for licensed practitioners who want to build their peptide program on with a partner they can trust. Our compounds are manufactured in the USA with pharmaceutical-grade processes, multi-layer testing, and full batch documentation on every order.
If you are a licensed practitioner ready to take sourcing seriously, we would be glad to connect.
This is not medical advice. Statements are for educational purposes only. Statements or products are not intended to diagnose, treat, cure, or prevent any disease.
All products are labeled for Research Use Only.
Want Deeper Insights into Emerging Peptide Research?
Join our newsletter for early insights into emerging blends, research developments, and strategies shaping the future of peptide therapy.