A certificate of analysis is useful only when the sample, method and reporting basis match the purchase agreement. Buyers should read the document as part of an inspection system, not as an isolated list of numbers.
Identify the shipment and sample
The COA should identify the product, lot or shipment, sampling date and test date. Check whether the sample represents production, a stockpile, loading or a destination inspection. A result from an unconnected sample cannot prove the quality of a specific shipment.
Confirm the basis of each result
Coal and carbon-material results may be reported on different bases. Moisture can change the relationship between as-received and dry-basis values. Ask the laboratory or supplier to state the basis clearly, especially when comparing fixed carbon, ash and volatile matter across offers.
Review the complete purchasing set
For Zhonghao’s catalog semi coke reference, the main fields are fixed carbon, volatile matter, moisture, sulfur, phosphorus, ash and particle size. Buyers may require extra fields for a particular furnace or alloy. Those additions should be listed in the RFQ rather than assumed after shipment.
Sampling can be the largest source of disagreement
Bulk material is not perfectly uniform. A representative method normally requires increments from defined locations or time intervals, followed by sample reduction and preparation. The contract should state who samples, whether sealing or joint witnessing is required and which version of the agreed method applies.
Separate chemistry from size inspection
Particle-size distribution requires its own sampling and sieving procedure. State the nominal range, fines threshold, oversize threshold and the point of measurement. Transport and handling can change size distribution, so dispatch and destination results may not be identical.
Prepare for an out-of-specification result
Before shipment, agree the retest laboratory, retained-sample procedure, acceptable tolerance and commercial remedy. This is much easier than negotiating a method after a dispute occurs.
COA review checklist
- Product, lot and shipment identity
- Sampling location, date and responsible party
- Test method and reporting basis
- Units, limits and actual results
- Laboratory identity and report date
- Particle-size method and fines/oversize results
- Retained sample and dispute procedure
A COA supports procurement confidence when it is connected to a representative sample and a written acceptance plan.
Source register
- Zhonghao formal product catalogue, page 1, Semi Coke technical index
- Industry method background: 煤的元素分析, https://mp.weixin.qq.com/s/TEWRQA2s970Cba9atX6vDA
- Industry standard background: GB/T 3499-2023 reference overview, https://mp.weixin.qq.com/s/D2vIiR8upTxRkaolfkHShA