How to read a certificate of analysis

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A certificate of analysis (COA) is a laboratory's written report on a specific sample. It is the single most useful document a research supplier can publish, and also the one most often misread. This guide walks through the parts of a typical certificate and what to check.

What a certificate is, and is not

A COA reports what a laboratory observed when it analyzed one sample from one lot using stated methods. It is evidence about that sample. It is not a general statement about a product name, and it is not a warranty about a different lot that happens to share the name.

Three consequences follow:

1. A certificate without a lot number cannot be tied to anything and should be treated as decorative.
2. A certificate for a different lot than the one on your vial tells you about a different sample.
3. A summary figure lifted from a certificate onto a product page has lost the context that makes it meaningful.

The parts of a certificate

Header and identification

The header identifies the laboratory, the client who submitted the sample, and the sample itself. Look for:

• Laboratory name and contact details. An independent, third-party laboratory should be identifiable and contactable.
• Report or certificate number. Unique to this document.
• Sample description and lot number. This should match the label on the vial exactly.
• Dates. When the sample was received and when the report was issued.

Methods

Each result should name the analytical method used to obtain it. Common methods on peptide certificates include high-performance liquid chromatography (HPLC) for purity and mass spectrometry (MS) for identity. The method section tells you how a number was produced, which is what makes the number interpretable.

Results and acceptance criteria

Results are usually presented in a table with, for each test, the specification or acceptance criterion and the observed value. Read them together: a result only means something relative to the criterion it was measured against.

Signatures and authorization

A certificate is normally signed or electronically authorized by the analyst and a reviewer. This is the laboratory taking responsibility for the content.

Checking a certificate against a vial

When a certificate is published alongside a compound entry on this site, it is identified by the internal Red Fern lot number. To check it:

1. Read the lot number printed on your vial label.
2. Confirm the same lot number appears on the certificate.
3. Confirm the issuing laboratory and the report date.
4. Read the method used for each result before reading the result itself.

If any of these do not line up, treat the certificate as not applying to your vial and ask.

Terminology

Term	Meaning
Lot	A quantity of material produced or received together and documented under one identifier.
Sample	The portion of a lot actually submitted to the laboratory.
Purity	The proportion of the sample that is the stated material, as measured by the stated method.
Identity	Confirmation that the material is what it is labeled as, typically by mass.
Acceptance criterion	The range or limit a result is compared against.

Further reading

The Quality & Testing page describes how Red Fern moves material from receipt to release and when certificates are published.