Chemistry
CAS Number
Research use only. For in vitro research use only. Not for human or animal consumption. Not for human consumption, medical use, or personal application.
A CAS Registry Number is an identifier assigned by the Chemical Abstracts Service to a specific substance, written as digits in three hyphenated parts ending in a check digit. It is a label, not a measurement: it fixes which substance is meant and says nothing about the quality of any lot. Its value is being unambiguous where names are not.
What the number leaves open
It identifies a registered substance, which for a peptide usually means a defined sequence in a defined form. Purity, salt form, water content and whether the vial holds what its label claims are lot questions, answered by the Certificate of Analysis.
Form matters more than it first appears. A free base and its trifluoroacetate salt are different substances with different masses, and the salt may carry its own number or none. Confirm salt form on the lot record.
Why some research peptides have no usable number
Registration follows the literature Chemical Abstracts indexes. Newer sequences, blends and modified analogues may have no number, one that belongs to a variant, or one of uncertain provenance copied between supplier catalogues.
For a blend the concept does not apply at all: a multi-component material is not one substance, so components are identified individually. Where no number exists, sequence and molecular weight carry the identification.
Frequently asked questions
- Can a registry number confirm two suppliers' material is the same?
It confirms they describe the same substance, not that the two lots are comparable. Purity, salt form and residual water differ between lots and manufacturers, and that comparison needs two certificates.
- Why do catalogue and certificate numbers sometimes disagree?
Usually because one refers to the free peptide and the other to a salt or a close analogue. Resolve it against the sequence and the measured mass before assuming an error.
- Is a registry number needed to order or ship research material?
Procurement and shipping systems ask for one because their records are substance-indexed. Where a sequence has no registry entry, the sequence and its calculated mass serve instead.
Updated 2026-06-01