GHK-Cu Molecular Weight, CAS Numbers and the Copper Complex

Buyers looking for GHK-Cu peptide in Canada tend to hit the same snag once the paperwork arrives: the numbers do not seem to agree. One document gives a mass near 340, another near 403, and the registry number on a listing may not match the one in a reference database. None of this necessarily signals a problem with the material. It comes from the fact that GHK-Cu is a small peptide bound to a metal ion, and the peptide and the complex are described separately. This guide sorts out the names, masses and registry entries, then covers what a QC team should check on a volume order.

GHK-Cu peptide in Canada: one tripeptide, several names

The same material is sold and published under a handful of labels:

• GHK refers to the tripeptide glycyl-L-histidyl-L-lysine on its own.
• GHK-Cu and copper peptide refer to that tripeptide bound to a copper(II) ion.
• Copper tripeptide-1 is the name used in the cosmetic ingredient literature for the copper complex.

GHK itself was first identified in human plasma and has been studied in cell culture and biochemical work for decades, largely because of its strong affinity for copper. What a lab receives in a vial labelled GHK-Cu is the complex, and the rest of this article is about describing it correctly.

Free tripeptide versus copper complex

The registry and most reference sources treat the free peptide and the complex as different substances, each with its own entry.

When a certificate and a listing appear to disagree, the first question is which column each is describing. A document quoting 340 for a GHK-Cu vial may simply be reporting the peptide portion, which is often what an HPLC-MS method detects.

Why listings quote different masses for the complex

Copper(II) binds GHK through the nitrogen atoms of the glycine amine, the histidine ring and a backbone amide, and binding displaces at least one proton from the peptide. How a supplier writes the formula depends on how many protons it treats as displaced and whether it counts associated counter-ions such as acetate or chloride. Different conventions give slightly different masses, usually within a few daltons of 403, and a salt-inclusive figure can be noticeably higher.

For a buyer this is a paperwork issue rather than a chemistry one. The practical fix is to note which convention a certificate uses and to compare like with like across lots. Our related article on GHK-Cu coordination chemistry goes deeper into how the copper is held.

Two tests, not one: peptide purity and copper content

An HPLC purity figure describes the peptide portion: what share of peptide-containing material is intact Gly-His-Lys rather than truncated sequences, deletion products or synthesis by-products. It does not measure the copper. The acidic mobile phases used in reversed-phase HPLC can also strip copper from the peptide during the run, so the chromatogram is effectively looking at free GHK.

Copper content is a separate measurement, usually by an elemental technique such as ICP-OES, ICP-MS or atomic absorption. As a reference point, in a 1:1 complex with no counter-ions or water, copper accounts for roughly 15.8% of the mass (63.5 out of about 402.9). Real material carries water and often a counter-ion, so the measured figure will normally sit somewhat lower. A copper result far below that range points to excess free peptide; a result well above it points to unbound copper salt.

Both numbers belong in a complete picture. A vial with excellent peptide purity but little copper is good GHK, not good GHK-Cu.

What the mass spectrum should show

Mass spectrometry gives GHK-Cu a distinctive fingerprint when the complex survives ionisation. Natural copper is a mix of two stable isotopes, copper-63 and copper-65, in roughly a 69:31 ratio. Copper-containing ions therefore appear as a pair of peaks two daltons apart, with the lighter one larger. Seeing that pattern is good evidence the complex is present. Under acidic LC-MS conditions, though, the free tripeptide signal near 341 ([M+H]+) is often the dominant one, and that is expected rather than a fault.

Colour is a useful secondary check too. The copper complex is blue, and a lot that turns out white or colourless deserves a closer look before it goes into use. Colour is not a quantitative test, but it costs nothing to record.

Planning a volume order: vial sizes and blends

We stock GHK-Cu in 50mg and 100mg vials, shipped from within Canada. For a programme that will run for months, fewer, larger vials from one lot keep all of your data under a single certificate and reduce the number of containers to receive, log and store.

GHK-Cu is also the largest component by mass in two blends: GLOW 70mg (with BPC-157 and TB-500) and KLOW 80mg (the same three plus KPV), each containing 50mg of GHK-Cu. If a project needs GHK-Cu at independent concentrations, use the single-compound vials. Because volume pricing is mix-and-match, single vials and blends in the same cart all count toward the volume break.

Receiving checks for GHK-Cu

1. Confirm the powder is blue and record its appearance with the lot.
2. Note which mass convention the certificate uses, free peptide or complex, and record it.
3. Look for a copper content result as well as HPLC purity; record whether one was reported.
4. Match each vial’s cap and crimp colour to its certificate and log the vial count per lot.
5. Store cold, dry and away from light, and keep reducing agents and strong chelators away from analytical samples, since both can disturb the copper.

Our products are third-party tested for purity by HPLC. Certificates are published for some products on the certificates of analysis page, and the purity guarantee page sets out what we commit to.

GHK-Cu is supplied by Bulk Peptides only for in-vitro laboratory research. It is not for human or animal use, and this article is not guidance on any such use.