How to read a certificate of analysis

A certificate of analysis is a record of what a specific laboratory measured, on a specific sample, on a specific date. It is not a general statement about a product line, and it is not a quality guarantee. Reading one well starts with checking that the batch identifier on the document matches the batch identifier on the container in front of you.

The header should name the testing laboratory, the date of analysis and the analytical method used. If any of these are missing, the document cannot be independently interpreted. A report that names a method such as HPLC-UV or LC-MS allows a reader to understand the limits of what was measured — no single method characterises everything.

The results table reports measured values against a stated specification. Pay attention to the specification column: a result can sit inside a wide specification and still differ materially from another supplier's result under a narrower one.

Finally, check the scope statement. Most reports explicitly limit their conclusions to the submitted sample. That limitation is the reason batch-level documentation matters more than a single historic report reused across a catalogue.