How to read a certificate of analysis

A certificate of analysis is a report from a laboratory stating what it measured in a specific lot of material, and by what method. It is not a claim by the seller. The value of a certificate comes entirely from being independently checkable: a lot number that matches the vial in hand, a lab that can be identified and contacted, and a method a reader can evaluate rather than take on faith.

The document types

Not every certificate reports the same thing, and a single lot can carry more than one.

• Purity states the fraction of the material that is the intended compound, by the stated method. This is the figure most often quoted on a product page.
• Content & identity confirms what a preparation contains and that it matches the labeled compound, which matters most for blends and salts rather than a single research peptide.
• Endotoxin reports bacterial endotoxin levels, relevant to any material intended for laboratory use with cell cultures or animal models.
• Heavy metals and microbial reports cover contamination testing outside the compound's own identity: a metals panel and microbial load, respectively.

A report that states amounts while explicitly excluding a purity figure is not a contradiction — some certificates are scoped to one of these categories and say so plainly.

Purity against label claim

A purity percentage describes the measured material, not the vial's total contents. Separately, some certificates state a measured mass against the label's stated amount — what the industry calls overfill, where a manufacturer fills slightly over the labeled quantity to offset losses in the fill process. Where a certificate states both figures, they answer different questions and neither substitutes for the other.

Lot tracking

A certificate is issued against one manufacturing lot, not one product. The lot or batch number on the certificate has to match the number printed on the vial for the document to say anything about the material in hand — a certificate for a different lot of the same compound verifies nothing about your vial, however similar the numbers look.

Why the lab matters

A certificate is only as good as the lab that signed it. An independent, named, contactable laboratory — one with no commercial stake in the result — is what turns a document into evidence. A certificate with no lab named, or one issued by the seller itself, is not independently verifiable and should be read as such.

Finding the current certificate

Every certificate we hold is published, searchable by lot or by compound, at the certificate index. A product page links directly to the certificate for its current lot; older lots stay in the index rather than disappearing when a new one is issued.