Reading a COA

A certificate of analysis (COA) is the lab report behind a product. Most sellers in this market post one. Far fewer buyers know how to read one. This lesson fixes that.

What a COA is

A COA is a document from a testing lab stating what it found when it analysed a sample. It should describe one specific batch, tested on one specific date, by one identifiable lab. If any of those three are missing or vague, the document tells you less than it looks like it does.

The parts that matter

Lot or batch number. The single most important line. It ties the report to a specific production run. The lot on the COA should match the lot printed on what you receive. No lot number means you can’t connect the report to anything you actually hold.

Lab name and contact. You should be able to tell who did the testing and how to reach them. Accredited labs often reference ISO/IEC 17025, the international standard for testing-lab competence.

Test date. Tells you how old the result is. A years-old report attached to a “fresh” batch is a mismatch worth asking about.

Identity — mass spectrometry (MS). Confirms the compound is what the label says by measuring its molecular mass. Look for an observed mass close to the expected value.

Purity — HPLC. High-performance liquid chromatography separates the sample and shows what share of it is the main compound. Usually shown as a percentage, ideally with the chromatogram (the graph of peaks) attached.

Quantity — content per unit. Some reports measure how much compound is actually present versus what the label claims. A product can be pure and still underfilled. Not every COA includes this.

Endotoxin and sterility. Separate tests. Endotoxin results are usually reported in EU (endotoxin units). A purity result says nothing about either.

Purity is not identity

This is the most common misread. A high HPLC percentage tells you the sample is mostly one thing. It doesn’t tell you which thing. That’s what the mass spec result is for. A COA with purity but no identity confirmation is only half a report.

What a COA can’t tell you

• Whether the product was stored and shipped properly after testing.
• Whether the unit in your hands came from the tested batch (that’s what the lot match is for).
• Anything the lab didn’t test for. If it isn’t on the report, it wasn’t checked.

Red flags

• No lot number, or the same COA used for every batch.
• No lab name, or the “lab” is the seller itself.
• A purity figure with no chromatogram or method listed.
• Dates, product names or quantities that don’t match the label.
• A lab you can’t find or contact.
• Edited-looking documents: mismatched fonts, misaligned numbers, blurred sections.

How to verify one

1. Match the lot number on the COA to the product label.
2. Find the lab independently (not through the seller’s link) and confirm it exists.
3. Check whether the lab or a third-party registry lets you look the report up by code.
4. If anything doesn’t line up, ask the seller. How they answer tells you a lot.

The checklist

• Lot number present and matches the label
• Identifiable, independent lab
• Recent test date
• Identity confirmed (mass spec)
• Purity with chromatogram (HPLC)
• Quantity tested, if the report claims it
• Endotoxin/sterility, if relevant to you
• Verifiable outside the seller’s own site

Next up: a good COA is only half the picture. The next lesson, Vetting a vendor, covers how to check the seller behind it.