Every agrochemical certificate of analysis (COA) should report active content, measured by a named method, for the specific batch. Beyond that, the tests depend on whether the product is a technical or a formulation, and on the formulation type.
A COA that shows only active content is not enough. Impurities decide the safety of a technical, and physical properties decide whether a formulation works. Agree the test list in your specification before the first order, so every COA follows it. For the basics of reading any COA, see what a certificate of analysis is.
Tests for a technical
- Active ingredient content is measured by a validated HPLC or GC method against the minimum purity in your specification.
- Each relevant impurity named in your registration is reported against its maximum limit.
- Water content is measured, usually by Karl Fischer titration.
- Acidity or alkalinity, or pH, is reported where the specification includes it.
- Insoluble material in the stated solvent is reported where it applies.
- Isomer ratio is reported for actives sold as a defined mix of isomers.
Tests for formulations
Formulations add physical tests, usually by CIPAC methods. The set depends on the type.
- An EC needs emulsion stability and re-emulsification, persistent foam and flash point.
- An SC needs suspensibility, pourability, wet sieve residue, particle size and persistent foam.
- A WP needs suspensibility, wettability, wet sieve residue and persistent foam.
- A WDG needs dispersibility, suspensibility, wet sieve residue, dustiness and attrition resistance.
- An SL needs a check that the solution stays clear on dilution, plus pH and density.
- Most liquids also report density, and many report pH and viscosity.
Details the COA itself must carry
- It shows the product name, batch number, manufacturing date and expiry or retest date.
- It names the test method for each result, with the specification limit beside it.
- It names the lab and carries the signature of an authorised analyst or quality manager.
- It gives a clear pass or fail against your specification, not the factory's own.
- It refers to the specification version, so you know which limits were applied.
Checking the COA against reality
A COA is a factory statement. Match the batch number with the drums or packs, and compare results across lots. Identical figures on every certificate are a warning sign. Our guide on checking a COA is genuine covers the method.
For important lots, have samples drawn at the factory by someone you trust and tested by an independent lab. Test at least active content and one or two key impurities or physical properties. The results show whether the factory's lab and yours agree.
Keep a retention sample from each lot. If a complaint arrives months later, you can test the same material.
Agree in your contract which lab result wins if the factory and the independent lab disagree. A common approach names an umpire lab in advance, with the method and the tolerance for differences between labs.
Next step
We draw samples at the factory, have lots tested independently and compare the results with the supplier's COA. Book a free sourcing review to set your test plan.