How to read a certificate of analysis (COA)

What a COA is

A certificate of analysis is a document from a testing lab that reports results for one specific batch (lot). A good COA ties a lot number to test results, a test date and the lab that ran them.

The parts to check

• Compound name and the amount per vial the batch is sold as
• Lot or batch number, which should match the label on your vial
• Purity, usually a percentage from HPLC (high-performance liquid chromatography)
• Identity, usually confirmed by mass spectrometry (MS): the measured mass should match the expected mass
• Test date and the name of the lab
• Sometimes: measured amount per vial, endotoxin or sterility results

Purity vs. identity

These answer two different questions. Identity asks: is this the right molecule? Purity asks: how much of the contents is that molecule? A high purity number means little if identity was never confirmed, so look for both.

In-house vs. third-party testing

Some vendors test their own products; others send samples to an independent lab. Third-party results are generally easier to trust, and some labs let you verify a report on their website with a report number or code.

Red flags

• No lot number, or a lot number that does not match your vial
• The same COA reused across many batches or products
• No lab name or test date
• Purity reported with no identity test
• A report the lab cannot verify when the lab offers verification

How The Pep Planner handles it

When you add stock in The Pep Planner you can attach a photo or PDF of the COA, and the app fills in the compound, amount, purity, lot and vendor it finds for you to check. The lot stays with that stock item, so when you mix a vial later you know exactly which batch it came from.

Common questions

Is a higher purity number always better?

Higher purity means less of the vial is something else, but only if identity was confirmed and the report matches your lot. Read the whole COA, not just one number.

What if my vial has no COA?

Ask the vendor for the report that matches your lot number. Note in your records that the batch had no COA so you can compare later.