For providers · 2 min read
How to read a certificate of analysis
The document that separates a supply chain you can defend from one you are trusting. Six fields, and one question that matters more than the rest.
A certificate of analysis is the record of what testing a specific batch of material passed. It is the single most useful document in a supply relationship, and it is routinely skimmed for the word "pass" and then filed.
Here is what is actually on it, and what each field is doing.
Identity
Confirms the material is the molecule it claims to be, usually by mass spectrometry. This is the field that answers "is this the right compound at all" — a question that sounds paranoid until you have seen a mislabelled shipment.
Purity
Typically by HPLC, reported as a percentage. Two things worth noticing: the method should be named, and the figure should be for this batch rather than a specification the batch is assumed to meet. A specification is a promise; a result is a measurement.
Water content
Matters for lyophilized material, because residual moisture affects stability over time. A low number here is part of why a freeze-dried vial can sit on a shelf.
Endotoxin
Bacterial endotoxin testing, reported against a limit. For anything intended for injection this is not optional, and a certificate that omits it is incomplete rather than reassuring.
Residual solvents
What is left over from synthesis. Reported against limits; the interesting case is a solvent listed but not quantified.
Batch and date
The lot number, the manufacture date, and a retest or expiry date. This is the field that makes the rest of the document mean anything.
The question that matters more than any single field: is this the certificate for the lot I actually received?
A specimen certificate — a representative example from some earlier batch — is not the same document, and it is remarkably common. It is also easy to check: match the lot number on the certificate against the lot number on the vial in your hand. If they do not match, you have a sample of somebody else's testing.
What to do with it
- Ask for it before you order, not after. A supplier who can produce it on request has a system; one who has to go and find it does not.
- Give it to whoever carries the clinical risk in your practice. If there is a medical director, this document is for them.
- Keep it. It is the record that ties a specific patient's material to a specific tested batch.
- If you want it independently verified, send it to a third-party lab. Any supplier who discourages that has told you something.
