GHK-Cu is sold under one name and supplied in at least two materially different forms, and the difference is not cosmetic — it changes what a milligram figure means, what a purity number is describing, and what you should expect a certificate to show. This page covers what is in the vial, how to check that it is what the label says, and what we supply in the USA.
What is GHK-Cu?
GHK is a tripeptide — glycyl-L-histidyl-L-lysine, three residues, nothing more. GHK-Cu is that same tripeptide carrying a coordinated copper(II) ion. They are two different substances with two different registry numbers and two different masses, and both are legitimately called “GHK-Cu” by somebody selling something.
The copper is not an impurity and it is not an additive. It is held by the peptide at specific coordination sites, and the resulting complex is the material most buyers are actually looking for. The two registry numbers and what each mass refers to works through the arithmetic; the coordination chemistry covers where the copper sits and why that geometry matters in the laboratory.
GHK or GHK-Cu: which one are you buying?
This is the first question to settle, and the certificate usually answers it if you know where to look. Three signals, in order of reliability:
- The mass on the mass spectrum. The free tripeptide and the copper complex differ by tens of daltons. A spectrum reporting the free-peptide mass is describing free peptide, whatever the label says.
- The registry number on the certificate. Two numbers exist. Which one appears tells you which material was characterised.
- The colour of the solid. The copper complex is blue. Free GHK is not.
If a supplier cannot tell you which of the two is in the vial, that is itself the answer to a different question.
What does a 50 mg or 100 mg figure refer to?
To the mass of material in the vial, not to the mass of peptide, and for a copper complex the gap is larger than most people expect. The figure includes the coordinated copper, the counter-ion, and residual water — none of which are the peptide.
Two separate corrections apply. The counter-ion is part of the isolated salt and contributes mass; TFA and acetate counter-ions covers what changes between the two forms. Residual water in a freeze-dried solid is commonly a few percent and is measured rather than assumed, by Karl Fischer titration — water content in lyophilized peptides goes into that measurement. The figure that accounts for all of it is net peptide content, and it is the number most often missing from a certificate. Net peptide content explained sets out the arithmetic.
Purity of a complex is not purity of a peptide
An HPLC purity figure is an area percentage: the main peak divided by the total area the detector recorded. For a copper complex that statement needs two qualifications.
The first is the detection wavelength, and it is the single most useful thing to check on any peptide certificate. Analysis run at 214 nm or 220 nm detects the peptide bond itself, so anything peptidic appears. Analysis run at 280 nm detects only tryptophan, tyrosine and weakly phenylalanine — and GHK contains none of those. A high purity figure obtained at 280 nm on this sequence is not a meaningful result. The wavelength is printed on the chromatogram.
The second is that a complex can partially dissociate on the column depending on the mobile phase, so the chromatogram may show the complex, the free peptide, or both, and the split between them is a property of the method as much as of the sample. Two laboratories can therefore return different figures for the same vial without either being wrong. Why two certificates can disagree works through the usual causes, and reading an HPLC chromatogram covers what a shoulder on a main peak actually indicates.
The colour is a real analytical signal
The blue of a copper(II) complex is not decorative. Its presence, and its depth, carry information about whether the copper is coordinated as intended, and a change in colour over time is a change in the material. A solid that arrives noticeably paler than expected, or a solution whose colour shifts on standing, is telling you something before any instrument does. It is the cheapest check available and it requires no equipment.
Storage and handling
Lyophilized material is hygroscopic: a vial opened cold and left open gains water from the air, and that water is mass that is not peptide. Allow vials to reach room temperature before opening, close them promptly, and keep them dark — light, oxygen and temperature covers the degradation routes that matter. Weighing lyophilized peptides covers why a balance reading drifts upward while you are taking it.
Copper complexes have buffer incompatibilities that free peptides do not. Strong chelators will compete for the metal, and some common buffer systems will not leave the complex intact. Choosing a reconstitution solvent covers the general problem; the coordination article covers this compound specifically.
What a certificate does not establish
A standard identity and purity certificate is silent on sterility, on endotoxin, and on anything concerning suitability for use in a person or an animal. Those are separate tests, they are not part of routine peptide characterisation, and their absence on a certificate is not an oversight — they were not run. Endotoxin, sterility and the limits of research grade is the longer version. Reading a purity figure as a safety statement is the most common misreading of these documents.
Buying GHK-Cu in the USA
We ship across the United States from within the country, so orders do not cross a border and are not subject to import processing. Carrier and service are chosen at checkout — USPS, UPS or FedEx, regular or express — with orders dispatched within one business day and typical transit of two to five days depending on destination and service.
Every certificate we hold is published in full on the certificates of analysis page, reproduced as the laboratory issued it rather than summarised into a figure. Certificates are not shipped with orders; a vial is matched to its certificate by cap and crimp colour against the photographs on the report itself. Third-party versus in-house testing explains why who selected and submitted the sample changes what a report establishes.
Sizes we supply
Two vial sizes, same material, same documentation:
- GHK-Cu 50 mg — the smaller vial, and the sensible choice where method development means a vial will be opened repeatedly. Fewer entries per vial means less cumulative moisture uptake.
- GHK-Cu 100 mg — better cost per milligram where the working quantity is already established.
GHK-Cu is also a component of two blends we supply, KLOW 80 mg and GLOW 70 mg. A blend vial carries its own considerations, because a single purity figure for a multi-component vial describes something different from a single-component one — purity and composition in a blend vial covers what to ask for.
All material is supplied for laboratory research use only. It is not a drug, not a supplement, and not for use in humans or animals.
