Every consignment of an industrial chemical should be traceable to a tested batch. The certificate of analysis (COA) links the two: it records what the batch was tested for, the method used and the result. Read properly, it tells you in a few minutes whether the material suits your process.
COA, SDS and specification sheet
| Document | What it tells you | Changes with each batch? |
|---|---|---|
| Certificate of analysis (COA) | Measured results for one specific batch against agreed limits | Yes |
| Safety data sheet (SDS / MSDS) | Hazards, safe handling, storage, first aid and transport information, in 16 sections | No — revised when the information changes |
| Specification or technical data sheet | The limits or typical values a grade is sold against | No |
You need all three, but only the COA says anything about the material actually in front of you. Our product catalogue includes specification sheets and safety data sheets for many of the products we handle.
The fields to check, in order
- Product name and grade — the exact grade, not just the chemical name. Check the CAS number as well.
- Batch or lot number — it must match the labels on the drums, bags or tank seals you receive.
- Dates — the date of manufacture or testing, and a retest or expiry date where the product has one.
- Test parameters and methods — each parameter should name its method: an ASTM, ISO or IS standard, or the producer’s in-house method.
- Limits and results — the specification limit beside the measured value, with units.
- Conclusion and sign-off — a pass statement and the name or signature of whoever released the batch.
Parameters that matter for common products
| Product | Parameters usually reported |
|---|---|
| Phenol | Purity (assay), freezing point, water content, colour |
| Methanol | Purity, water content, acidity, colour, permanganate time, specific gravity |
| Acetone | Purity, water content, acidity, non-volatile residue, colour |
| Formaldehyde solution | Formaldehyde content, methanol content, acidity (as formic acid), iron |
| Paraformaldehyde | Formaldehyde content, water, ash, physical form |
Colour is usually given on the platinum-cobalt (APHA or Hazen) scale and water by Karl Fischer titration. If your process is sensitive to a parameter that is not on the certificate, ask for it to be added before you place the order — not after the material arrives.
Warning signs
- Results written only as “conforms” or “passes”, with no measured values.
- No batch number, or a batch number that does not match the packaging.
- Results identical to the last decimal across several different batches.
- No test methods stated, or a certificate dated long before the shipment.
- A grade on the COA that differs from the one on your purchase order.
None of these proves a problem on its own, but each is a reason to ask questions before the material goes into production.
Make the COA part of the order
The most reliable approach is to agree the specification — parameters, limits and test methods — at the enquiry stage and reference it on the purchase order. Ask for the COA with the dispatch documents, keep a retained sample from each delivery, and compare results over time. Our quality page explains how documentation is coordinated with each supply.
