Two documents describe the quality of a commodity cargo. The specification sheet says what the seller undertakes to deliver. The certificate of analysis (COA) says what a laboratory found in one lot. Buyers lose money when they treat the first as proof and the second as a promise. This guide explains how to read both.
Four documents that get confused
| Document | Issued by | What it is |
|---|---|---|
| Specification sheet | Seller or producer | The limits the product is sold to. A contract term once it is attached to the contract. |
| Technical data sheet (TDS) | Producer | Typical properties and uses. Usually not a guarantee. |
| Certificate of analysis (COA) | Producer's laboratory or an independent inspector | Results for a named lot or cargo. |
| Safety data sheet (SDS) | Producer | Hazards, handling and transport classification. Says little about commercial quality. |
A producer's COA shows what left the plant. An independent inspector's certificate, drawn from samples taken at loading, shows what went on the ship. Contracts and letters of credit should name the second.
Guaranteed or typical
Look for the column heading. "Guaranteed", "specification" or a plain minimum or maximum is a commitment. "Typical" is an average of past production and commits the seller to nothing. A sheet that gives only typical values has not told you what you can reject.
Each guaranteed line should have three parts: the property, the limit with its direction, and the test method.
- Urea: nitrogen 46.0% min; biuret 1.0% max; moisture 0.5% max; granules 2 to 4 mm 90% min.
- White sugar ICUMSA 45: polarisation 99.80° min; colour 45 ICUMSA units max; moisture 0.04% max.
- Bitumen 60/70: penetration at 25°C 60 to 70 dmm; softening point 49 to 56°C; flash point 250°C min.
A number without "min" or "max" is not a limit.
The basis changes the number
The same material gives different figures depending on how the result is reported:
- Coal. Calorific value is quoted gross as received (GAR), net as received (NAR), or air dried (ADB). A coal of 5,000 kcal/kg GAR is roughly 4,700 NAR. Ash and sulphur are quoted as received, air dried or dry. Comparing a GAR offer with a NAR offer without converting overstates one of them by several percent.
- Ores and concentrates. Iron, silica and alumina are reported on a dry basis; the cargo is weighed wet. Payment is on dry metric tonnes, so moisture is a price term as well as a quality one.
- Grains and oilseeds. Protein is quoted at a stated moisture basis, commonly 12% or dry matter. Oil content in seeds may be "as is" or dry basis.
- Fertilisers. Phosphate is reported as P2O5 and potash as K2O, not as the element; total and water-soluble P2O5 are different lines.
If the basis is not printed beside the figure, ask before comparing prices.
The test method is part of the specification
Different methods give different results for the same sample. Sulphur in fuel by ASTM D4294, viscosity by ASTM D445, protein by Kjeldahl or by Dumas, sugar colour by ICUMSA method GS2/3-10: the method fixes what the number means. A specification should name the method for each property, and the COA should report results by the same methods. When they differ, the results are not comparable and a dispute has no reference.
Every method also has a stated precision. Two competent laboratories testing one sample will differ within the method's reproducibility. A result just inside or just outside a limit is not a clear pass or fail, which is why contracts provide for an umpire analysis.
Rejection limits and price scales
Many specifications carry two numbers for a property: a base and a rejection limit. Between them the price adjusts.
- Coal: base calorific value with a pro-rata price adjustment, and a rejection limit some hundreds of kcal lower.
- Iron ore: a price per dry metric tonne unit of Fe, penalties per 1% of silica and alumina above base, rejection below a stated Fe.
- Wheat: protein scales, and rejection limits for moisture, test weight and falling number.
Read both numbers. A cargo can be within the rejection limit and still cost you a penalty, or earn the seller a bonus.
What a certificate must identify
A COA that can be tied to your cargo shows:
- The lot or batch number, or the vessel name and bill of lading date.
- The quantity the sample represents.
- Where, when and how the sample was drawn, and by whom.
- The seal numbers of the retained samples.
- Date of analysis and the laboratory's name; accreditation to ISO/IEC 17025 for the tests reported is the usual standard.
- Each result with its unit, basis and method.
- A signature and a reference number that the issuer can confirm.
Signs a certificate does not belong to the cargo
- The analysis date is months before the shipment, or after the bill of lading date.
- No lot number, vessel name or sampling place.
- Every result is a round number, or matches the specification exactly.
- Methods are missing, or are not ones the named laboratory uses for that product.
- The inspector's logo appears but the certificate number cannot be confirmed with the inspector's office. Inspection companies verify their own certificates on request; use that before paying.
- The product described is not what the origin plant makes.
Before you sign
Attach the specification to the contract, state that the independent load-port certificate is the quality document, name the methods, and set out the price scale and the rejection limits. How the samples are drawn and which analysis is final are covered in our guide to inspection and sampling.
How CBIL works
We send the producer's specification with each offer and say which lines are guaranteed. Every cargo we arrange ships against an independent inspector's certificate from samples drawn at loading, and the producing plant is named on the certificate of origin.
Request a quote and attach or paste the specification you buy to.