How to Read a Magnesium Sulphate Certificate of Analysis
The Certificate of Analysis (COA) is the most important quality document in a magnesium sulphate shipment. It records what was measured in a specific batch, so buyers should know how to read it and what to question.
Header details
A proper COA identifies the product, grade, batch or lot number, manufacturing date, and the standard or method used. The batch number should match the bag markings and the commercial invoice. A COA with no batch number is a red flag.
Key parameters
| Parameter | What it tells you |
|---|---|
| Assay (as MgSO₄·7H₂O, or MgSO₄) | Overall purity of the product |
| MgO / Mg content | The nutrient or magnesium value you are paying for |
| Sulphur | Important for fertilizer buyers |
| pH (of a solution) | Consistency and process compatibility |
| Water-insoluble matter | Critical for drip irrigation and clear solutions |
| Chloride, iron | Impurities that matter in technical and food uses |
| Heavy metals (Pb, As, Cd, Hg) | Safety limits for food, feed, pharma and bath grades |
| Particle size | Whether the crystal size matches your order |
Watch the basis
Check whether figures are reported as heptahydrate or on a dry basis. The same material can look very different depending on the basis, and mixing them up leads to wrong comparisons between suppliers.
Supplier COA vs independent testing
A supplier's own COA is standard, but for new suppliers or high-value grades, buyers often add an independent laboratory test or a pre-shipment inspection. Our magnesium sulphate has been independently tested by the National Test House, a Government of India laboratory, and we share that report on request.
Need a quote for magnesium sulphate?
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