What is a CAS number?

What it is

A CAS Registry Number is an identifier assigned to substances by the Chemical Abstracts Service. The format is up to ten digits in three groups, e.g. "NNNNNNN-NN-N". Numbers are unique — one structure, one number — with no chemical meaning encoded in the digits themselves.

Why one peptide can have several numbers

Different forms of a substance — free base, acetate, hydrochloride, hydrates — are separate registry entries with separate numbers. For peptides this matters constantly: commercial materials are typically supplied as salts, and the correct CAS number depends on the actual form, which manufacturer documentation must confirm.

What a CAS number does not guarantee

The number identifies the substance as a concept, not the contents of a particular vial. It confirms neither batch identity, nor purity, nor quantity. A CAS number on a product card without analytical documentation is a statement of intent, not evidence.

This is why the Moscow Peptides catalogue states a CAS number only once the material's actual form is confirmed by its documentation. Where the form is unconfirmed, the field stays empty with a "pending confirmation" status — a deliberate accuracy policy.