A specialty chemical certificate of analysis should show a basic set of tests plus the figures that control performance for that product type. The base set is usually appearance, active content or solids, pH, viscosity, water content and colour.
Each line should show the test, the method, the specification limit and the actual result for that batch. For the general role of a certificate, see what a COA is.
The base tests
- Appearance describes the physical form and colour, such as "clear pale yellow liquid".
- Active content or assay shows how much of the working ingredient is present, often by titration or chromatography.
- Solids content shows the non-volatile part of an emulsion or solution, measured by drying a sample.
- pH is usually measured on a stated dilution, such as a 1% or 10% solution, which the certificate should name.
- Viscosity must state the instrument, spindle or method, speed and temperature, or the number cannot be compared.
- Water content is often measured by Karl Fischer titration for liquids and by loss on drying for powders.
- Colour is given on a named scale, such as APHA (Hazen) for pale liquids or Gardner for darker ones.
Tests by product type
Surfactants and ethoxylates often add ionic nature, cloud point, hydroxyl value, acid value and free fatty alcohol or unreacted material. Cosmetic grades add limits on impurities such as 1,4-dioxane, heavy metals and microbial count.
Emulsion binders and adhesives often add particle size, minimum film-forming temperature, residual monomer and free formaldehyde where relevant. Water-treatment chemicals add active content for the named species, such as alumina in PAC, plus iron and insoluble matter. Powders often add bulk density, particle size by sieve and flow properties.
Agree the list in your specification, so the certificate reports exactly what you need.
What makes a certificate useful
The result should be a real number, not "complies" or "passes". You need the number to track trends from batch to batch.
The certificate should name the batch, manufacturing date, expiry or retest date, the plant and the person who approved it. It should match the batch number on the packs and the shipping documents.
Methods should be recognised where possible, such as ISO, ASTM, or national standards. In-house methods are fine if the supplier shares them, so your laboratory can repeat the test.
Check that the certificate is genuine and belongs to your batch. See checking a chemical COA is genuine for the method.
What a certificate does not prove
A certificate confirms the tests listed on it, measured by the supplier. It does not prove performance in your process, and it does not cover tests that were never run. For high-value lots, have an independent laboratory test a correctly drawn sample before shipment.
Also remember that a certificate is only as good as the sample behind it. A result measured on a sample drawn from the reactor before filling may not reflect what reached the drums. Ask where and when the sample was taken.
Next step
We agree certificate contents with the plant, check each certificate against the batch, and have lots tested before loading. Book a free sourcing review.