Use this COA and specification comparison framework to prepare a clearer RFQ, compare supply options and reduce avoidable changes between sampling, quotation and shipment.
Core principle: A compliant result requires the tested method, unit and limit to match the agreed specification.
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Certificate of analysis versus specification
A specification and a certificate of analysis (COA) are often confused, but they do different jobs. A specification defines the acceptance criteria — what “good” means. A COA reports what a specific sample actually measured. One sets the target; the other reports a result against it.
Side-by-side comparison
| Factor | Specification | Certificate of analysis (COA) |
|---|---|---|
| Purpose | Defines acceptance criteria | Reports test results for a sample |
| Created by | Agreed between buyer and supplier | Issued by a laboratory |
| Applies to | The product, going forward | The specific sample or lot tested |
| Contains | Parameters, limits, methods, tolerances | Measured values against parameters |
| Answers | “What must the product meet?” | “What did this sample measure?” |
How they interact
The specification defines the parameters and limits; the COA reports the tested lot’s values against them, and acceptance is the comparison of the two. A COA without an agreed specification has nothing to be judged against.
Common mistakes
- Treating a supplier’s COA as if it were the specification.
- Accepting a COA that does not report the parameters your specification requires.
- Assuming a COA for one lot proves future lots conform.