A certificate of analysis is only worth its test methods
A phosphate COA turns up in every transaction and is read properly in very few. The difference between a certificate that can be enforced and one that is a piece of paper is four specific things, and most certificates in circulation are missing two of them.
The four things
1. Identification of the lot. A COA without a lot or batch number cannot be tied to the material in the bag. A surveyor will say so, and a buyer has no way to prove that the certificate describes the cargo rather than a previous production run.
2. The test method for each figure. “P2O5 46%” is an assertion. “P2O5 46.2%, citrate-soluble, AOAC 963.03” is a measurement. Only the second can be argued with, and only the second is any use when the buyer’s laboratory returns a different number.
3. The distinction between available and water-soluble P2O5. These are different quantities and both matter. Available P2O5 is what the plant can access over time; water-soluble is what dissolves immediately. A certificate that reports one figure without saying which it is has created the conditions for a dispute.
4. Issue by the plant, not the trader. A certificate from a trading company about material it did not make is worth very little. Under a letter of credit it can be worse than nothing, because if the credit calls for a producer’s certificate and a trader’s certificate is presented, the documents are discrepant and the payment stops.
What a complete phosphate COA reports
For a bulk grade:
- Product name and grade
- Lot / batch number and production date
- Total nitrogen, where applicable
- Available P2O5, with method
- Water-soluble P2O5, as a percentage of available
- Moisture
- Granule size distribution
- Crushing strength
- Free acid, for superphosphates
- Bulk density, if specified
For a soluble grade, replace granule size and strength with water-insoluble residue, pH, and appearance.
For a feed or food grade, add the regulated impurity suite: fluorine, arsenic, lead, and whatever else the destination requires. Those are not quality indicators; they are the figures that decide whether the cargo may legally be used.
A typical value is not a guarantee
There are three kinds of number on a certificate, and confusing them is how disputes start.
Typical — what the product normally runs. Useful for evaluation, useless in a contract.
Guaranteed minimum — what the supplier commits to. This is the number that belongs in the contract.
Measured — what this lot actually tested at. This is the number on the COA.
A contract written against a typical value is unenforceable, because the supplier never promised it. A contract written against a guaranteed minimum is enforceable, and the COA is the evidence.
Turning a COA into a specification
The practical move is to take the desired COA and convert it into contract language:
| On the COA | In the contract |
|---|---|
| P2O5 46.2% | Available P2O5: 46% minimum, citrate-soluble |
| Water-soluble 89% of available | Water-soluble P2O5: 85% minimum of available |
| Moisture 1.2% | Moisture: 1.5% maximum |
| 2–4 mm, 94% | Granule size: 90% minimum within 2–4 mm |
| Free acid 0.8% | Free acid: 1.0% maximum |
Note what changed. The measured value becomes a limit with a tolerance, and the method is named. That is a specification. The COA alone is a snapshot.
The TDS and the MSDS
TDS describes the product rather than the lot: typical analysis, physical properties, solubility, storage and handling, recommended use. It is what a customer evaluating the product wants, and what a registration dossier is built from.
MSDS covers transport classification, handling, first aid and disposal. For solid phosphate fertilizers it is short, because they are not dangerous goods. For phosphoric acid it is not short: UN 1805, Class 8, corrosive, with the packaging and carrier requirements that follow.
What not to accept
- A COA with no lot number
- A COA with no test methods
- A COA where P2O5 has no stated basis
- A COA issued by anyone other than the plant
- A COA that has been edited
Any of those is a reason to ask again, and the answer to “can you alter it” is always no. If the material does not meet the specification, the solution is different material.
This guide describes documentation practice. For the documents a specific shipment will carry, confirmed item by item, ask the export desk.
Questions buyers ask
Who should issue the COA?
The producer, for the specific production lot. A certificate issued by a trading company rather than the plant is worth very little at the port, and in a letter of credit context it is worse than nothing because it creates a documentary discrepancy.
What is the difference between a COA and a TDS?
A COA is lot-specific and reports measured results for that material. A TDS describes the product in general — typical analysis, physical properties, storage and handling — and is what you send to a customer evaluating the product, or use to build a registration dossier.
Can a COA be altered?
It should never be. A trader-issued or altered analysis that does not come from the plant is worthless at the port and, under a letter of credit, constitutes a documentary fraud risk. If the material does not meet the specification, the answer is different material, not a different certificate.
Need a price for a specific cargo?
Give us the product, grade, quantity and discharge port, and the quotation comes back with the specification basis stated.