A certificate of analysis, or COA, is the document that reports test results for one specific batch of a chemical. It shows that the batch meets the agreed specification, test by test.
The COA is batch-specific. That is what sets it apart from the technical data sheet, which shows typical values for the product in general.
What a proper COA shows
- The name and address of the company issuing it, and whether it is the manufacturer or a separate lab.
- The product name, grade and CAS number where relevant.
- The batch or lot number, the manufacturing date and the expiry or retest date.
- Each test parameter, such as assay, moisture, pH, colour or impurities.
- The test method for each parameter, by standard number or in-house method reference.
- The specification limit and the actual result for each test, side by side.
- A clear pass or conforms statement.
- The date of testing and the name and signature of the person who approved it.
Manufacturer COA versus third-party COA
Most COAs come from the manufacturer's own quality control lab. That is normal, and a good plant's lab is often well equipped. But it is the seller testing its own goods.
A third-party COA comes from an independent lab that tested a sample drawn from the batch. It costs time and money, so buyers usually use it for first orders, high-value lots or critical parameters. If you use one, make sure the sample was drawn by someone independent, not handed over by the plant. Our article on reading a lab certificate explains what to look for in a lab report.
What a COA cannot tell you
A COA only covers the tests listed on it. If your specification does not include a heavy metal limit, the COA will not report heavy metals, and the batch may still contain them.
A COA also says nothing about whether the batch in the drums is the batch that was tested. Linking the two needs sampling at loading, sealed retention samples and matching batch numbers on drums, COA and packing list. See how to check a COA is genuine.
Using the COA well
Agree the COA format before the first order. List every test you need, with method and limit, in the purchase contract. Ask for the COA before the goods are loaded, not with the shipping documents. That gives you time to query a result before the container leaves.
When to ask for more than a COA
For routine repeat orders of a stable product from a plant you trust, the manufacturer's COA plus periodic independent testing is usually enough. Ask for more on first orders, after a change of process or site, for products with tight impurity limits, and whenever a previous lot caused a problem. In those cases, an inspector should draw samples at the plant and send them to an independent lab before the goods are loaded. The cost of that test is small compared with the cost of a rejected container at your port.
Next step
We review each COA against your specification and have lots tested independently when it matters. Book a free sourcing review.