How to read a Certificate of Analysis

A COA is the only document that tells you what is actually in a vial. Most buyers never read one properly, and most sellers are counting on that. This takes about four minutes and applies to every supplier you will ever deal with, including us.

What a COA is, and what it is not

A Certificate of Analysis is a laboratory's report on a specific batch of material. Not on the product line. Not on the company. On one batch, tested on one date.

That distinction is the whole point. A supplier who tested one good batch in 2023 and has been sending that same PDF ever since has a COA. They do not have quality control. The lot number and the test date are what separate the two, which is why they are the first two things to look for.

Identity and purity are different questions

People use "tested" as if it means one thing. It means at least two.

Question	Usual method	What it actually proves
Identity Is this the right molecule?	Mass spectrometry (MS), sometimes written LC-MS or MALDI-TOF	Measures molecular weight and compares it to the expected value. Catches the case where you were sold something else entirely.
Purity How much of it is the right molecule?	High-performance liquid chromatography (HPLC)	Separates the sample into its components and reports each as a percentage of the total. Catches the case where you were sold the right thing, heavily diluted.
Appearance	Visual	Colour and form. Weak on its own, but a mismatch is a genuine warning.
Water content	Karl Fischer titration	How much of the stated weight is water. Relevant because you are usually buying by mass.

A document reporting purity with no identity test is not enough. It tells you the sample is 99% something. Both belong on the same certificate.

The anatomy of a real certificate

1. Lot or batch number It must match the number on the vial you receive. If you cannot match them, the document is decoration.
2. Date of analysis Recent, and after the manufacturing date. A COA older than the product is a copied document.
3. Name of the testing laboratory An actual named third party with a findable address. "Tested in-house" is not third-party testing — it may be honest, but it is a different claim and should be labelled as one.
4. Method stated for each result "Purity: 99%" with no method is a number someone typed. "Purity: 99.1% by HPLC" is a measurement.
5. The chromatogram or spectrum itself The actual trace, not just the summary figure. This is the raw evidence and the hardest thing to fake convincingly. Its absence is not automatically damning, but its presence is a strong signal.
6. A signature or analyst identifier Someone's name is attached to the result.

Red flags

What a COA cannot tell you

Worth being clear about, because certificates get treated as a universal guarantee and they are not.

• It says nothing about safety or effect. A COA reports composition. That is all it reports.
• It says nothing about handling after testing. A pure batch stored badly for six months is still backed by a genuine certificate.
• It covers the batch tested, not necessarily the vial in your hand — unless the lot numbers match. Which is why they are the first thing to check.

The short version