COA literacy
How to Read a Certificate of Analysis
A certificate of analysis (COA) documents specific tests on a specific batch. Read it field by field — and keep four measurements distinct: identity (which molecule), purity (relative composition), potency/assay (activity), and quantity (how much). They are not interchangeable.
The fields
- 1Material / product name The substance the report describes — not proof the sample matches it.
- 2Batch / lot number Ties results to one specific production lot. Must match the material in hand.
- 3Report / COA number The certificate's own identifier, used for verification and traceability.
- 4Laboratory information Who performed or issued the analysis; needed to judge independence.
- 5Report / test dates When the sample was received and tested — context and traceability.
- 6Identity result Which molecule is present, established by an identity method (e.g. mass).
- 7Purity result Relative detected composition under the stated method — not identity or quantity.
- 8Potency / assay / quantity How much / how active — a distinct measurement from purity and identity.
- 9Analytical method The technique and conditions; every result must be read against its method.
- 10Specifications / acceptance criteria The pre-set thresholds a result is compared against.
- 11Additional analytical checks Any further tests actually performed (only what is listed was done).
- 12QR code / verification A pointer to verify the report against the issuer's records.
Not interchangeable
Identity, purity, potency and quantity measure different things
Identity
Which molecule is present. Established by an identity method such as mass — not by a purity figure.
Purity
The relative detected composition under the stated method. Says nothing on its own about identity or amount.
Potency / assay
How active the material is. A distinct measurement from composition.
Quantity
How much is present. Not implied by purity or identity.
What to look for
Reading a COA carefully
- Confirm the lot number on the COA matches the material you are evaluating.
- Check that the analytical method is named for every reported result.
- Look for identity established by an actual method (e.g. mass), not inferred from purity.
- See whether a chromatogram or supporting data is included, not just a number.
- Note the report and test dates, and whether the laboratory is identifiable.
- Read each result only against the specification stated for it.
Common misinterpretations
What a COA does not establish
“A high purity number proves identity”
Purity is relative composition under a method; identity is a separate measurement.
“Purity means the material is safe or fit for use”
A COA is analytical documentation, not a statement of safety or suitability.
“Purity, potency and quantity are the same thing”
They answer different questions — composition, activity, and amount.
“If one test passed, everything was tested”
Only the tests actually listed were performed.
“A COA with any lab name is independently verified”
Independence and identifiability of the lab still need checking.