How to Read a Certificate of Analysis (COA)
When you buy a chemical or liquid product, the label tells you what's supposed to be in the bottle. A Certificate of Analysis (COA) shows what testing actually found. Here's what a COA is, how to read one, and how to find the COA for your Compass Laboratory bottle.
What is a Certificate of Analysis?
A COA is a document that reports test results for one specific batch, or lot, of a product. It confirms that the batch was tested and shows whether the results met the required specifications. Because every batch is tested separately, each COA is tied to a single lot number.
The main sections of a COA
COA layouts vary between labs, but most include the same core information:
| Section | What it tells you |
|---|---|
| Product name | The material that was tested, sometimes with its chemical name or CAS number. |
| Lot / batch number | The specific batch the results apply to. This should match the lot number on your bottle. |
| Dates | Manufacture, test, or release dates, plus the expiration or retest date. |
| Test (parameter) | What was measured, such as appearance, identity, assay (purity), or specific impurities. |
| Method | How the test was performed, often referencing a standard such as a USP method. |
| Specification | The acceptable range or limit the batch must meet. |
| Result | The actual value measured for this batch. |
| Pass / conforms | Whether each result fell within its specification. |
| Approval | The signature or sign-off from the person or lab that reviewed the results. |
How to read the results
The most useful part of any COA is the comparison between Specification and Result. For each test, check that the result falls inside the stated range. A few terms you'll see often:
- Assay: how much of the main ingredient is present, usually as a percentage. For example, a specification of "98.0% to 102.0%" with a result of "99.6%" means the batch passed.
- Identity: confirms the material is what it claims to be.
- Conforms: the result matched the expected description or standard.
- ND (not detected): the substance was below the level the test can detect.
- < (less than): the result was below a stated limit, such as "< 10 ppm."
- ppm: parts per million, a common unit for trace impurities.
Red flags to watch for
- No lot number, or a lot number that doesn't match the product label.
- Results listed without specifications, so there's nothing to compare against.
- Missing dates or no sign-off from the testing lab.
- A single generic COA used for every batch a seller has ever made.
How to find the COA for your Compass Laboratory bottle
- Find the lot number and expiration date printed on your bottle.
- Visit our Our Standards & Certificates of Analysis page.
- Select the lot number that matches your bottle to view its COA.
Don't see your lot listed? Contact us and we'll send the COA directly to you.
Why we publish our COAs
Every Compass Laboratory batch gets its own lot number so it can be traced from production to your door. Publishing our COAs means you don't have to take our word for what's in the bottle. You can check the results yourself.
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This article is for general educational purposes only.