How to read a certificate of analysis

A certificate of analysis (COA) is a record of what an analytical laboratory measured on one specific lot of material, on one specific date. It is not a marketing sheet and it is not a general description of a compound. It answers one question: what was in this lot when it was tested?

On our quality page we describe the standard behind every lot: testing is performed by a third-party laboratory with no commercial interest in the result, purity is measured by HPLC, identity is confirmed by mass spectrometry, and the certificate is published with the lot before it is listed. The certificate is the document that makes those statements checkable.

Each certificate names the compound, the lot number, the assay date, the analytical method and the measured purity. Read them in that order.

• Compound. The name of the material tested. It should match the label on your vial exactly, including any suffix or salt form printed there.
• Lot number. The single most important line. A certificate describes one lot only; a certificate for a different lot of the same compound tells you nothing about yours.
• Assay date. When the laboratory ran the analysis. A certificate is a snapshot of that day, not a promise about the future.
• Analytical method. What was done to get the number — for purity, that is HPLC; for identity, mass spectrometry. The method tells you what the result can and cannot mean.
• Measured purity. The result the laboratory recorded, as a percentage. How that percentage is derived is worth understanding on its own; see what HPLC purity actually measures.

Before reading anything else, find the lot number printed on your vial and find the lot number on the certificate. They must be identical. Material is released by lot and nothing is blended between lots after testing, so the number on the vial always maps to a single assay — that is the point of lot discipline.

If the numbers do not match, stop. Either you are looking at a certificate for a different lot, or something is wrong with the shipment. In either case, contact support with the number on the vial and the certificate will be sent the same business day.

A purity figure without a method is just a number. HPLC purity is a chromatographic measurement: it tells you how much of what the detector saw belonged to the main peak. Mass spectrometry confirms identity: it tells you the material has the molecular mass expected of the named compound. Together they answer "is this what it says it is, and how clean is it?" Separately, each answers only half of that question.

That is why a certificate that shows a purity result with no identity confirmation, or an identity result with no purity, should prompt a question to the supplier. Ours carry both.

A certificate describes the lot on the day it was tested. It does not describe what happens to the material after it leaves the laboratory — storage, handling, temperature excursions and time all sit outside the document. Storage conditions and lot stability data are stated on the certificate itself, and those conditions are the researcher's responsibility from the moment the parcel arrives.

It also does not describe any application. Nothing we publish, including the certificate, describes a preparation, a dilution or a use. All material is supplied for in-vitro laboratory research only — see research use only.

File the certificate where you file the material. A lab that can produce, for any vial on the shelf, the certificate for that exact lot is a lab that can answer any question an auditor, a reviewer or a colleague asks. If you need a certificate for a lot you already hold and cannot find it, contact support with the lot number.