How to read a certificate of analysis
Purity, identity, method and lot: what each field on a COA means and what to check before you open a vial.
Dr. Elena Varga
Head of Quality · · 6 min read
Overview
A certificate of analysis (COA) documents the results of analytical testing for one specific lot. It is only meaningful when the lot number on the certificate matches the lot number on your vial.
What to check
Purity is usually reported from HPLC as a percentage of the main peak area. Identity is confirmed separately, typically by mass spectrometry, which checks that the molecular weight matches the expected compound.
In practice
Check the analysis date, the laboratory, and the storage conditions. A certificate without a lot number or method should not be trusted.