A certificate of analysis (COA) is the manufacturer’s record that one specific lot was tested and met its specification. A usable COA names the manufacturer and the lot, and gives three things for every test: the limit, the measured result and the method. If any of those is missing, the document cannot support a supplier qualification.
What should be on it
| Section | What to look for |
|---|---|
| Product identity | Name, grade and CAS number matching your purchase specification |
| Manufacturer | The name and address of the site that made the lot, not only the seller |
| Lot number | A unique number that also appears on the drum label |
| Dates | Manufacture date and retest or expiry date |
| Test table | Each test with its limit, result and method |
| Standard cited | The monograph and its edition, for example the current USP |
| Sign-off | Name, title and date from the quality unit |
Reading the test table
Identity. At least one test that confirms the material is what the label says: infrared spectrum, HPLC retention time or a compendial identification test.
Assay. How much of the active substance is present. Check the basis. “On the dried basis” and “as is” give different numbers, and some ingredients are assayed as another compound: riboflavin 5′-phosphate sodium is reported as riboflavin, so a conforming result is 73–79%.
Physical tests. Appearance, loss on drying, specific rotation, particle size. Specific rotation confirms the correct isomer for chiral ingredients such as L-theanine.
Contaminants. Lead, arsenic, cadmium and mercury, with a numeric result or a stated reporting limit. Residual solvents where they could be present. Microbial counts where the specification includes them.
Results should be numbers
“Conforms” is acceptable for a pass-or-fail test such as identification. It is not acceptable for an assay or a heavy-metal test. A column of “conforms” against quantitative tests suggests the lot was not measured, or that the seller copied the specification.
Warning signs
- The manufacturer is not named, or is described only as “our factory”.
- Results are identical across different lots.
- Every result sits exactly at the limit or is a round number.
- The certificate is on a trader’s letterhead with no reference to the original.
- The monograph cited is out of date or does not exist for that ingredient.
- The lot number on the document does not match the label on the container.
A COA does not replace your own testing
For U.S. dietary supplement manufacturers, 21 CFR 111.75 requires at least one appropriate identity test on every lot of a dietary ingredient, whatever the certificate says. You may rely on the supplier’s COA for other specifications only after qualifying the supplier by confirming its results, and you must re-confirm periodically.
That is why the test methods matter. If your laboratory cannot reproduce a result because the method is not disclosed, the certificate cannot be verified.
Read more about what we send in our document pack.
This article is general information for business customers. It is not legal or regulatory advice. Confirm requirements for your own products with qualified counsel or a regulatory consultant.