CAS numbers for research peptides

The CAS number on a peptide specification is a small piece of metadata that does a surprising amount of work: it is the unambiguous identifier that survives naming chaos, it is what customs, safety systems and literature databases key on, and a mismatched or absent CAS number is a useful early warning about a supplier. This note explains what CAS numbers are, how to use them for research peptides, and their limits. All Alphex products are for laboratory and in-vitro research only.

What a CAS number is

A CAS Registry Number is a unique identifier assigned by the Chemical Abstracts Service to a specific substance. It has the form XXXXXXX-XX-X, with the final digit a checksum. It identifies a substance, not a name: a compound with six trade names and three development codes has one CAS number, and searching on it retrieves everything indexed for that substance regardless of what the source called it.

The Alphex catalogue's numbers

• BPC-157: 137525-51-0
• TB-500 (Ac-LKKTETQ): 885340-08-9
• GHK-Cu: 49557-75-7
• Ipamorelin: 170851-70-4
• GLP-3 (RT) / retatrutide (LY3437943): 2381089-83-2
• Bacteriostatic water: 7732-18-5 (water) and 100-51-6 (benzyl alcohol)

What to use them for

• Literature searching. Databases index by CAS, so a search retrieves papers that use a development code you have never heard of.
• Cross-checking a supplier's listing. If the name and the CAS number do not describe the same substance, something is wrong: either sloppiness or a different compound. This is a fast check to run before ordering.
• Institutional systems. Chemical inventories, COSHH records and waste manifests are usually keyed by CAS. See record keeping.
• Customs and shipping declarations. Accurate identification speeds clearance for international orders. See importing research peptides.

Limits

• Salt forms and hydrates may share or differ in CAS number depending on registration. The number will not tell you whether a peptide is the acetate or TFA salt; the specification must. See acetate versus TFA.
• Stereochemistry is registered, so a D-containing peptide and its all-L counterpart have different numbers, but a supplier quoting the right number is not evidence that the vial contains the right isomer. See D-amino acids and unnatural residues.
• Complexes: GHK-Cu's number refers to the copper complex; free GHK has its own. See GHK versus GHK-Cu.
• A CAS number is not a quality claim. It says what the substance is meant to be, nothing about purity, identity verification or handling.

Using it as a supplier check

Take the CAS number from a listing, look it up, and confirm it matches the compound name, molecular formula and molecular weight also given. Mismatches, missing numbers, or a number that belongs to a related but different compound (the full-length protein rather than the fragment, the free peptide rather than the complex) are all findings. Combine with the checks in what a compliant listing looks like.

Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.

Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.

Published 2 April 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.

Alphex Research Team

Alphex Limited, UK research peptide supplier

The Alphex research team writes and maintains these notes for UK laboratories buying research peptides. Every batch Alphex lists is verified by reverse-phase HPLC with a batch-matched Certificate of Analysis. Content covers laboratory and in-vitro research only.