Every consignment of a food or pharma grade chemical should arrive with a certificate of analysis. It is the producer’s statement of what that particular batch actually tested at. Used properly it is the difference between accepting a pallet and discovering a problem three weeks into production.
The mistake we see most often is treating the COA as a formality — checking that one exists, filing it, and moving on. A COA is only worth anything if you read it against the specification you bought to.
What a certificate of analysis is
A COA reports results for a specific, identified batch. That is what separates it from a technical data sheet, which describes the product in general terms and gives typical or guaranteed ranges. The TDS tells you what the product is; the COA tells you what this batch measured.
If a document gives you ranges rather than single measured values, you are looking at a specification sheet, not a certificate of analysis. Both are useful. They are not interchangeable.
The fields that matter
- Batch or lot number. This must match the number printed on the sacks or drums you received. If it does not, the certificate belongs to different material.
- Date of manufacture. Combined with the shelf life, this tells you how much usable life the material has left when it reaches you — not when it left the producer.
- Assay or purity. The headline number. Check the test method as well as the figure; the same nominal purity measured by different methods is not always comparable.
- Appearance. Sounds trivial, but a mismatch here — granular where you expected fine powder — is the earliest warning that the wrong grade has shipped.
- Loss on drying / moisture. Often the field that determines whether a hygroscopic material will cake before you use it.
- Heavy metals and residual limits. Frequently reported as “conforms” rather than a number. If your own specification sets a limit, ask for the measured value.
Three things buyers routinely miss
Typical values presented as batch results. Some certificates repeat the same figures batch after batch. If every COA for a product shows an identical assay to two decimal places, you are being sent typical values on certificate letterhead.
The retest date rather than the expiry. Many inorganic salts do not expire so much as require retesting after a period. A retest date is not a use-by date, and treating it as one wastes usable material.
Test methods left unstated. “Assay 99.5%” means little without the method. Where the specification you are buying to names a method, the certificate should name the same one.
Check it on arrival, not at point of use
Match the batch number on the certificate against the batch number on the packaging before the pallet is put away. It is a two-minute check at goods-in and it catches the errors that are expensive to unpick later — mixed batches on one pallet, a certificate for the previous shipment, or a grade substitution nobody flagged.
Keep the certificate with the intake record for that batch. When a customer complaint arrives eighteen months later, the ability to trace a finished lot back to the raw material batch and its certificate is what turns a guess into an answer.
What to ask for when you order
State on the purchase order which documents you require and in what form. If you need the certificate before the goods ship, say so — it is much easier to resolve a discrepancy while the material is still with the producer.
We supply the certificate of analysis with every consignment, and technical data sheets and safety data sheets are available on request. If you have a house specification you buy to, send it with your enquiry and we will check the producer’s specification against it before the order is placed.
Browse the catalogue or send us an enquiry with the product, grade and quantity you need.
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