How to read a certificate of analysis without guessing

A certificate of analysis (COA) is the part of the paperwork that most people open first and understand least. It is a short document, but each line answers a different question, and mixing those questions up is the most common source of confusion at the bench.

Start with the identity block

The top of the sheet should name the material, the lot number and the date of analysis. Check these three against the label on the vial before anything else. If a lot number on the sheet does not match the vial in your hand, stop there and contact the supplier. Everything below depends on that match.

Separate what was measured from what was declared

Declared values describe what the batch record says was filled. Measured values describe what the analysis found. They are not the same thing, and a good COA shows both with the method used for each measurement. Look for the words used to describe the method, not only the number.

• Declared net fill, as stated on the lot record
• Measured content, with the technique named
• Date of analysis and the laboratory that performed it
• Any stated limits or acceptance criteria

When a field is blank

A blank field is information too. It may mean the test was not run for that batch, or that the result is held in a separate report. Ask which one it is, in writing, and keep the reply with the lot record. Your notebook should show that you asked, not only that you received the sheet.