Most confusion around this ingredient is not a chemistry problem, it is a paperwork problem. The same three amino acids — glycine, histidine, lysine — are sold both on their own and bound to a copper ion, and the two forms carry different CAS numbers, different molecular weights, different INCI names and different colours. Then a third term, “copper peptide”, is used as a generic label across several unrelated materials. If your specification only says one of these words, it does not yet describe a lot you can verify. At Demeter Biotech we supply the copper complex — Copper Tripeptide-1, CAS 89030-95-5 — as a 1 g lyophilized bottle, and the CAS and INCI name are stated on the lot documents so there is nothing to interpret.

1. Three labels, two molecules

Start with the only distinction that matters commercially: one of these materials contains copper and one does not. GHK is the free tripeptide. GHK-Cu is that tripeptide holding one copper(II) ion. They are related, they are not interchangeable, and they do not weigh the same. A purchase document that names only “GHK” may be describing material with no copper in it at all.

2. “Copper peptide” is a family name, not an identity

The third label is the loosest one. “Copper peptide” is trade wording rather than a defined substance, and under it you can be quoted at least three kinds of material that share nothing but a marketing category:

• Copper tripeptide-1 — the Gly-His-Lys copper complex, CAS 89030-95-5. This is the material most cosmetic formulators mean.
• A different copper-binding sequence — for example AHK-Cu, built from a different three-amino-acid order, used in hair-care work. Same category name, different molecule, different CAS.
• A copper salt with no peptide at all — such as copper PCA. Copper plus an organic acid; nothing tripeptide about it.

The practical consequence is simple: a quote line or a certificate that reads “copper peptide” gives you no figure you can check. Ask for the INCI name and the CAS number before you compare prices, because two quotations at the same price per gram can be describing two materials that differ by nearly a fifth of their mass.

3. The 18% you cannot skip

Because the two molecules differ in mass, a formula written in percentages does not transfer between them. The complex weighs about 401.91 g/mol; the free peptide weighs 340.38 g/mol. Divide one by the other and the complex is roughly 1.18 times heavier for the same peptide chain — which means one gram of GHK-Cu carries about 0.847 g of GHK backbone, with the balance being the copper and the lost protons in the coordination.

This is not a subtlety for the laboratory only. If a brief asks for a set molar amount of the peptide and the material on the bench is the complex, you need about 18% more of it by mass to land on the same number of moles. If a brief is written as “1% GHK” and the factory weighs out 1% GHK-Cu instead, the peptide content delivered is lower than the writer expected. Neither error is visible on the label; both show up later as a formula that will not reproduce. Quote both numbers — mass of material, and peptide content — and the ambiguity disappears.

4. Colour is a free identity check

There is one check you can make with your eyes before any instrument is involved. The free tripeptide is white to off-white. The copper complex is blue. That blue is not a dye or a colourant added afterwards — it is the visible-region absorption of the copper(II) ion held in its coordination sphere, and it is absent when the metal is absent. Equilibrium and spectrophotometric work on this system described the visible absorption spectra of the copper species directly, which is why the colour is read as a coordination signature rather than a cosmetic choice (Lau and Sarkar, 1981).

So a colourless or greyish powder offered under a copper-peptide name is worth a question, not an accusation. It may be the free peptide; it may be a copper salt blended with something else; it may be a complex that has lost its metal. In each case the resolution is the same document: the CAS number, the copper figure and the assay basis on the batch certificate.

5. The copper is held, not welded on

The reason the two forms are so easily confused is that they interconvert at the level of a single bond. The copper sits in a coordination sphere rather than being covalently locked into the peptide chain: the imidazole nitrogen of the histidine side chain, the alpha-amino group of glycine and the deprotonated amide nitrogen all participate, and the side-chain amino group of lysine measurably strengthens the complex relative to shorter analogues — a detail that came out of potentiometric and spectrophotometric speciation work on this exact tripeptide (Lau and Sarkar, 1981).

Because it is coordination and not a covalent modification, the metal can also be handed off. A later structural study showed GHK forming ternary copper complexes with albumin, with the metal shared between the peptide and a second ligand rather than held exclusively by one (Bossak-Ahmad et al., 2021). Read as formulation chemistry, that is the whole warning: anything in a formula that competes for copper — a chelating agent, a strong pH shift, a reducing agent — is competing for the same coordination site that defines the blue complex. Identity tells you what you bought; coordination tells you what it will still be after your formula is finished. We take up the pH and chelation questions separately in this series.

6. Four lines that end the ambiguity

Write these four fields into the specification and the naming problem stops being a risk. They also make two quotations comparable for the first time, because they force both onto the same basis.

7. How Demeter supplies GHK-Cu

At Demeter Biotech we supply the copper complex only — Copper Tripeptide-1, CAS 89030-95-5 — as a cosmetic-grade lyophilized powder in 1 g bottles. It is the blue form, water-soluble, and each lot is released against a certificate of analysis that states identity, assay, copper content, heavy metals and microbiology, so the four fields above are answered before the bottle is packed. If your brief is written against the free peptide instead, say so and we will tell you plainly that it is a different material rather than ship a substitute. Send us the INCI name, the CAS number and the assay basis you need, and we will confirm the lot figures against your specification before you commit.

Blue Copper Peptide GHK-Cu Powder — Copper Tripeptide-1, Water-Soluble Cosmetic-Grade Active

Cosmetic-grade GHK-Cu supplied as a 1 g lyophilized bottle. Copper Tripeptide-1 (INCI), CAS 89030-95-5, water-soluble, released against a batch certificate covering identity, assay, copper content, heavy metals and microbiology.

View the specification →

Pure Blue Copper Peptide Powder GHK-Cu (CAS 89030-95-5) — Cosmetic Grade, 99% Tripeptide-1

High-purity cosmetic-grade GHK-Cu, CAS 89030-95-5, in a 1 g lyophilized bottle. Copper Tripeptide-1 (INCI), water-soluble; the batch certificate states peptide assay, copper content and the analytical method used.

View the bulk specification →

The name on a document should be a specification, not a category. Read the CAS number and the copper figure, and what you order is what you will receive.

This article describes molecular identity, nomenclature, mass relationships and documentation only. It is not a statement of efficacy or safety, and it does not describe any use other than as a cosmetic raw material. Molecular weights, CAS numbers and the calculated copper fraction are literature figures for the named compounds; the only numbers that bind a lot are those on its batch certificate of analysis. Trade category names such as “copper peptide” are not standardised and should always be resolved to an INCI name and a CAS number before comparison.