A Certificate of Analysis (COA) is a document issued by a supplier or laboratory that confirms a specific batch of product has been tested and meets its stated specifications. For chemicals, it lists the test results — purity, key impurities, physical properties — for the exact lot you are buying, signed off against the agreed specification. It is the proof that what is in the drum matches what you ordered.
This guide explains what a Certificate of Analysis contains, how to read each part, the difference between a COA and a Safety Data Sheet, and why you should always ask for one when buying chemicals.
What does a Certificate of Analysis contain?
A typical chemical COA includes:
- Product name and grade — the exact material and its grade (e.g. technical, food, USP).
- Batch / lot number — the single most important field. It ties the certificate to one specific production batch.
- Manufacturing and/or expiry date — when the batch was made and, where relevant, its retest or expiry date.
- Specification limits — the agreed acceptable range for each tested property.
- Actual test results — the measured value for each property in this batch.
- Test methods — the standard or method used for each test (e.g. titration, GC, Karl Fischer for water).
- Pass/fail or conformance statement — confirmation the batch meets specification.
- Authorisation — signature or approval from the quality department.
How to read a Certificate of Analysis
Reading a COA is mostly about comparing two columns: the specification (what the product should be) and the result (what this batch actually measured). Here is how to work through it:
- Check the batch number matches your delivery. The COA is only valid for the lot number printed on the containers you received. A COA for a different batch tells you nothing about your material.
- Confirm the product and grade are correct. Make sure it is the right chemical and the right grade for your application.
- Compare each result against its specification. For every property, the result should fall within the specification limit. For example, if purity is specified as “99.0% min” and the result is “99.4%”, that passes.
- Pay attention to the impurities that matter for your process. Water content, heavy metals, chloride, iron — the impurity limits are often more important than the headline purity, depending on what you’re doing.
- Check the date. For materials with limited shelf life, confirm the batch is within its retest or expiry window.
Example: reading a purity line
If a COA shows:
| Property | Specification | Result | Pass? |
|---|---|---|---|
| Assay (purity) | 99.0% min | 99.4% | ✓ Yes |
| Water | 0.1% max | 0.06% | ✓ Yes |
| Iron (Fe) | 50 ppm max | 12 ppm | ✓ Yes |
…then every measured value is within its limit, and the batch conforms.
COA vs Safety Data Sheet (SDS): what’s the difference?
These two documents are often confused but serve completely different purposes:
| Certificate of Analysis (COA) | Safety Data Sheet (SDS) | |
|---|---|---|
| Purpose | Proves a batch meets its quality specification | Tells you how to handle the material safely |
| Batch-specific? | Yes — tied to one lot number | No — applies to the product generally |
| Contains | Test results vs specification | Hazards, first aid, handling, storage, transport, disposal |
| When you need it | To verify quality of what you received | Before handling, for safety and compliance |
You should have both for any chemical you buy: the SDS for safe handling, and the COA to verify the specific batch meets specification.
Why a Certificate of Analysis matters when buying chemicals
A COA is your quality guarantee and your paper trail. It matters because it:
- Confirms you received what you paid for — the right purity and grade, not a cheaper substitute.
- Protects your process — an out-of-spec impurity can ruin a batch, damage equipment or cause a product failure downstream.
- Supports your own compliance — if you make food, pharmaceutical or regulated products, your auditors will expect COAs for your raw materials.
- Enables traceability — if something goes wrong, the batch number on the COA lets you trace and isolate affected material.
A supplier who cannot or will not provide a batch COA is a warning sign. Always ask for one.
Frequently asked questions
What is a Certificate of Analysis (COA)?
A COA is a document confirming that a specific batch of a product has been tested and meets its stated specifications. It lists the test results for that lot against the agreed specification.
What is the difference between a COA and an SDS?
A COA proves a specific batch meets its quality specification; an SDS tells you how to handle the material safely. The COA is batch-specific; the SDS applies to the product generally.
Is a Certificate of Analysis batch-specific?
Yes. A COA is only valid for the batch (lot) number printed on it. Always check the batch number on the COA matches the containers you received.
Who issues a Certificate of Analysis?
The manufacturer, supplier or an independent testing laboratory, authorised by their quality department.
Should I always get a COA when buying chemicals?
Yes. A reputable supplier provides a batch COA with every order. It confirms quality, supports your own compliance, and gives you traceability if anything goes wrong.
We issue a Certificate of Analysis with every order, for every product in our catalogue. Browse our chemical range or request a bulk quote — your COA is included.