Certificate of Analysis
What a Certificate of Analysis records.
A Certificate of Analysis (COA) is a document describing information about a specific lot of a material. For researchers, it is the link between a physical sample and its recorded characteristics.
Fields a COA may include
- Product / material name and chemical identity
- Lot or batch identifier
- Appearance or physical description
- Analytical results, where testing was performed
- Date of analysis and any storage or handling notes
Not every material ships with every field, and availability differs from product to product. Documentation availability is identified with the applicable product information rather than assumed.
Identity, assay, and limit tests
The analytical lines on a certificate rarely answer the same question. An identity test asks whether the material is the compound named on the label, and is usually satisfied by comparing a spectrum or a chromatographic retention against a reference; its outcome is a conformance statement rather than a number. An assay measures the proportion of the named substance present in a sample, and is only interpretable alongside the method used to obtain it. A limit test sets a ceiling instead of measuring a target — water content, residual solvent, or residue on ignition are reported as being at or below an agreed threshold. Reading all three as one undifferentiated block of numbers is the most common way a certificate is misread. Our note on how laboratories verify chemical identity covers the identity step in more detail.
Specification versus result
A specification is the acceptance criterion fixed before the analysis; the result is what the instrument produced. A certificate that reports results with no specifications cannot be judged pass or fail by the reader, and one that lists specifications with no results states an intention rather than an outcome. Both columns, set side by side and attributed to a stated method, are what make the document auditable after the fact.
The dates are not interchangeable
Date of manufacture, date of analysis, and any retest or re-evaluation date describe three different events, and conflating them is a frequent source of confusion. An analysis can post-date manufacture by a considerable margin. A retest date is a statement about when the issuing party would examine the material again under the storage conditions it names; it is not a guarantee of condition, and it says nothing about a container that has been opened or held differently. The assumptions behind those conditions are discussed in storing and handling research powders.
Who issued it, and for which lot
A certificate is only as traceable as the party that signed it and the lot identifier that anchors it. A document issued in-house by a manufacturer or repackager from its own analysis is a different kind of record from a report produced by a contract laboratory, and a certificate written for one lot does not carry over to another lot of the same material even when the two are visually indistinguishable. That is why the batch identifier is the field every other field depends on; see lot traceability in research supply.
Certificates and safety data sheets
The two documents answer different questions and neither substitutes for the other. A certificate describes what one specific lot was found to be. A safety data sheet describes the hazards associated with the substance and the precautions for handling, storage, and disposal that apply regardless of lot. A quality file generally keeps both, together with the identifiers that tie them to the same material.
Our commitment
We do not attach purity figures or testing claims to a lot unless documentation supports them for that specific lot. To learn more, read Understanding the Certificate of Analysis or review our Quality & Documentation approach.