GHK-Cu lab tests

Seven checks before you trust a GHK-Cu certificate

The same seven questions decide whether a certificate of analysis means anything, whichever compound it describes. Six are about the document; the seventh is about what no document can tell you.

1. An independent, batch-matched COA. The certificate must name the batch or lot in your hands, and must come from a laboratory the vendor neither owns nor pays. A specimen certificate from an earlier lot proves nothing about the vial you were sent.
2. HPLC purity, read against a known band. A purity figure is only informative against the distribution for that compound. "Above 98%" is not a claim — the useful question is whether the result sits inside the range the rest of the market reports. How to read HPLC and mass-spec results.
3. Mass-spectrometry identity. HPLC says how much of the sample is one thing; it does not say which thing. Only a mass-spec result establishes identity, and it is the only check that separates compounds a few daltons apart. Contamination is not hypothetical: research-grade custom peptides from two independent commercial suppliers were found to carry contaminating peptides at roughly 1% by weight, enough to produce false-positive results in immunology assays (Clinical and Vaccine Immunology, 2008 — a study of HIV vaccine peptide libraries rather than of any compound on this site).
4. Net content, measured rather than assumed. Purity and quantity are different questions: a vial can be 99.7% pure and still contain two thirds of the labelled mass. Why 10 mg isn't 10 mg.
5. Endotoxin (LAL) on the batch. An absent endotoxin line means the batch was not tested — not that it passed. Endotoxin testing and LAL interpretation.
6. Who ran the test, and what they left off. A laboratory with a record on this compound, named on the certificate, with a verification route back to it. Testing laboratories we track · Red flags in a certificate of analysis.
7. What no test on the vial can establish. A perfect certificate confirms that a vendor sold the correct molecule at the stated quantity. It says nothing about efficacy, dosing, or long-term safety.

Want a vial tested yourself? How to send a peptide for independent HPLC testing.

What GHK-Cu testing has to rule out: the copper-free peptide

GHK-Cu is sold as a 1:1 copper complex of the tripeptide glycyl-L-histidyl-L-lysine, weighing about 403 Da. The copper-free tripeptide weighs 340.38 Da, costs less to make, and passes an HPLC purity test perfectly. HPLC separates by hydrophobicity and reports peak area, not metal, so a sample of pure copper-free GHK returns an excellent purity figure. On this compound a high purity number is compatible with receiving exactly the wrong molecule, and a certificate carrying a purity percentage with no mass result has not addressed the question that matters.

Mass spectrometry settles it. The two candidates differ by roughly 62.5 Da, about 18% of the molecule: 340.38 for the free tripeptide against about 403 for the 1:1 copper complex. That gap is trivially visible on a mass spectrum and invisible to HPLC. A batch-matched spectrum reading near 403 Da is the copper complex; 340.38 is the copper-free peptide carrying the GHK-Cu name. The substitution risk is per batch, not per vendor. Elemental analysis would measure the copper directly at 1:1 stoichiometry, but Peptigrity has not seen it offered by any vendor or laboratory serving this market.

The purity records on this page cannot answer the copper question either: as of May 2026, none of the 736 independent HPLC tests then on file measured copper. The naming confusion starts in the reference databases, which hold three chemical records rather than two:

• GHK free tripeptide (Gly-His-Lys): PubChem CID 73587, C₁₄H₂₄N₆O₄, MW 340.38, CAS 49557-75-7.
• Cu-GHK (neutral adduct record): PubChem CID 378611, C₁₄H₂₄CuN₆O₄, MW 403.92, no CAS.
• Prezatide copper (monocation): PubChem CID 71587328, C₁₄H₂₃CuN₆O₄⁺, MW 402.92, CAS 89030-95-5. Copper-to-peptide stoichiometry is 1:1 across all copper records.
• PubChem's copper-free record (CID 73587) carries the synonyms "GHK-Cu", "Copper Peptide", "Copper(II)ghk", "Copper glycyl-histidyl-lysine", "Prezatide" and "Tripeptide-1" — six names for a copper complex attached to a molecule containing no copper. Treat any of them on a listing as ambiguous rather than confirmatory; a listing built from database synonyms can mislabel without intending to.
• A label or spec sheet printing 340.38 under a GHK-Cu heading has described the wrong molecule on its own packaging: 49557-75-7 is free GHK, 89030-95-5 is prezatide copper.
• Wikipedia's chembox for the copper complex gives C₁₄H₂₂CuN₆O₄ with CAS 89030-95-5, a formula matching none of the three PubChem records (PubChem's record for that CAS is the monocation C₁₄H₂₃CuN₆O₄⁺), and lists a different CID for free GHK than PubChem's own. A spec sheet reproducing those figures should be rejected.
• Peptigrity's GHK-Cu compound page flags that "some vendors sell free GHK labeled as GHK-Cu (mislabeling) or use suboptimal copper-to-peptide ratios." Mass spectrometry alone will not fully characterise a suboptimal ratio; that takes elemental analysis.
• Endotoxin (LAL) matters more here than on most compounds, because FDA's published concern about injectable GHK-Cu is specifically immunogenicity from aggregation and peptide-related impurities.