How formulators verify a peptide raw material before scale-up

A peptide raw material arrives as a few grams of powder, a certificate of analysis and, if you asked, a safety data sheet. Nothing about the powder tells you on its own whether it is the compound on the label, whether the purity figure was measured on that lot, or whether the seller made it. The paperwork can be checked and the powder can be tested, and both cost far less than finding a problem after a stability batch and a label print run.

This guide is the sequence a formulator can run on a first order without specialist equipment: resolve the identity on paper, collect the documents, place the supplier, then test the sample. Copper Tripeptide-1 (GHK-Cu) is the worked example because it so often arrives with two CAS numbers; the method is the same for any peptide powder you buy in bulk.

Why you verify before scale-up, not after

Verification matters more for peptides than for most cosmetic actives, for three reasons.

• Several identities share one name. A trade name, an INCI name and a laboratory abbreviation can point to different molecules, or to the same molecule with and without a metal or a counter-ion.
• Purity is method-dependent. An HPLC figure describes what one column and one detector could separate. Water, salts and counter-ions are invisible to it, so two certificates with the same figure can describe powders with different peptide content.
• The supply chain is long. Many sellers are resellers. The vial on your bench may have been repackaged and stored at room temperature on the way, and the certificate may have been issued for a different container.

The gap between paperwork and powder is documented. Verbeke and colleagues bought a set of synthetic peptides from commercial suppliers, each sold with a stated purity of at least 95.0%, and re-tested them in-house; they report that only 44.0% met the stated purity, that the main component of one sample had a different structure from the peptide ordered, and that most related impurities were missing one or more amino acids. They conclude that a buyer should not rely on the supplier's certificate alone (Verbeke F et al. J Pharm Anal, 2015).

You do not need every step for every reorder. You do need the whole sequence once per material and per source, and a record of it.

The four identity questions

Identity comes first because every later test compares the powder with an expectation, and the expectation has to be the right molecule.

1. Which name is on the paperwork?

• The INCI name is the name on the finished product's ingredient list in most markets: Copper Tripeptide-1, Acetyl Octapeptide-3, Palmitoyl Pentapeptide-4, Glutathione. It is recorded in the European Commission's CosIng database and belongs on your raw-material file.
• A trade name belongs to the company that first commercialised the ingredient and often describes a diluted solution or a blend rather than the pure peptide.
• A common name such as GHK-Cu, SNAP-8 or AEDG is laboratory shorthand with no regulatory meaning.

Ask the supplier to print the INCI name on the COA; if a compound has none, as with Epitalon, note that, since it changes how the ingredient is declared.

2. Which CAS number, and is there a second one?

A CAS Registry Number identifies one substance, and a salt, a hydrate or a metal complex of a peptide is a different substance from the free peptide. That is the whole trap.

Material	CAS	PubChem CID	Formula	Molecular weight (g/mol)
GHK-Cu, the copper(II) complex (the powder you normally buy)	89030-95-5	71587328	C14H23CuN6O4 (cation)	402.9
GHK, the copper-free tripeptide Gly-His-Lys	49557-75-7	73587	C14H24N6O4	340.4

Both numbers are correct for something. A seller who prints 49557-75-7 may be supplying the copper complex and copying the number from an older listing, or may be supplying the copper-free tripeptide and expecting you to add a copper salt yourself. The CAS number alone cannot tell you which; the mass-spectrometry line can. Salts of other peptides carry their own numbers or none, so for any peptide ask: which exact form is this number for, and does the powder match it?

3. Cross-check in PubChem and CosIng

• PubChem resolves a CAS number or a name to a record with a molecular formula, a computed molecular weight and a synonym list. Check that the synonyms include your INCI name, that the formula contains the metal or counter-ion you expect, and that the weight matches the COA. The copper complex is CID 71587328 and the free tripeptide is CID 73587.
• CosIng, the European Commission's cosmetic ingredient database, lists INCI names with their CAS numbers, reported functions and any restriction in the EU annexes. A CosIng entry is an inventory record, not an approval.

4. Does the molecular weight match the mass spectrum?

Take the molecular weight from PubChem for the exact form you ordered and compare it with the "found" value on the COA's mass-spectrometry line. For GHK-Cu the copper complex is seen near m/z 403 and the free tripeptide near m/z 341, a gap of about 62.5 (one copper atom replacing one proton). A COA that reports HPLC purity but no mass identity has not shown you which molecule the main peak is. Ask for the spectrum, or at least the expected and found values, before you pay.

What to ask the supplier for before paying

Ask for everything in one message, before the invoice. A manufacturer that tests every lot has it on file and sends it the same day. A reseller has to ask upstream, and the delay and the answer both tell you something.

• A lot COA with a lot number, and confirmation that the same number will be on the vial. A COA with no lot number is a specification, not a test report.
• The HPLC chromatogram, not only the figure: main peak, impurity peaks, retention time and the method header.
• The mass-spectrometry identity: the spectrum or at least the expected and found molecular weight.
• The SDS in the 16-section format, written for the powder and naming the same manufacturer as the COA.
• The manufacturer's name and physical address, as distinct from the seller's trading name.
• The retest date and storage statement. For the peptides on this site that is 2–8 °C for working stock and −20 °C long-term, protected from light.
• The counter-ion and water content, if not on the COA. Both affect how much peptide is in a gram of powder.

If any item is refused, decide now whether you can live without it.

How to tell a manufacturer from a reseller

Neither is wrong to buy from, but you should know which you are dealing with: it decides who can answer a technical question and whose records you rely on.

Look at the addresses

The COA and the SDS each name a company and an address. On a manufacturer's documents they are the same company and a production site. On a reseller's they are often a trading office in one country and a synthesis site in another, or the manufacturer's name has been replaced with the reseller's logo. Ask plainly: did you make this, and where? A reseller that names the manufacturer is being straightforward; one that will not answer is the problem.

Look at the batch numbering

A manufacturer's lot codes follow a system, with a prefix, a date element and a product element, running in sequence across the catalogue. A reseller's codes are often those codes with a prefix added, or an internal number that matches no upstream record. Ask what the lot code means; someone who runs the synthesis can decode it.

Look for public records

The strongest signal is whether lot records exist somewhere the seller cannot edit afterwards. Pepti, Guangzhou publishes its batch records at peptioem.com/coa, where each record carries the lot code, the HPLC purity figure, the test date and the certificate PDF; the published figures currently fall between 98.4% and 99.8%. Whichever manufacturer you use, the question is the same: can you find your lot in a record library, and does the figure there match the paper in your envelope?

A bench verification sequence for a 5 g sample

The minimum order on this site is 5 g of bulk powder, or a 10-vial sample kit as a first order. Either is enough to run this sequence, keep a retained portion and still have powder for trials. Work in order; each step is quick and each can stop you wasting the next.

1. Appearance. Let the container warm to room temperature before opening, to avoid condensation on a hygroscopic powder. Record colour, texture and clumping, and compare with the COA appearance line. Copper peptides are blue to blue-violet; most other cosmetic peptides are white to off-white. A white powder labelled as a copper complex, or a copper peptide that has turned green-grey or brown, is a reason to stop here.
2. Solubility. Weigh a small portion, add water, and note how quickly it dissolves, whether the solution is clear and whether anything remains. A palmitoylated peptide such as Palmitoyl Pentapeptide-4 is not expected to dissolve in water alone, so an insoluble result is only a finding when the material should have dissolved.
3. Colour of the solution for copper peptides. A GHK-Cu solution is clear and blue. Cloudiness, a colourless solution or a colour that drifts within an hour each point to a different material, a chelated or reduced copper, or an unstable lot.
4. pH of a solution at a fixed concentration. Make up a solution at a concentration you write down, measure the pH and record it. There is no target; the value depends on the counter-ion and the isolation route. Its use is comparison, lot against lot and source against source.
5. UV-visible scan. If you have a spectrophotometer, scan the same solution and keep the trace as a fingerprint to compare across lots. The scan does not measure purity.
6. Split the sample for independent HPLC. Send one portion to a contract laboratory for reverse-phase HPLC and, if the budget allows, mass spectrometry. Give the laboratory the method conditions from the supplier's chromatogram so the results can be compared, and ask for the chromatogram. Keep the other portion sealed at −20 °C as a retained sample.

Steps 1 to 5 can tell you that a sample is wrong. Only step 6 can tell you that it is right; the first five rule out gross errors before you spend money on the sixth.

Verification checklist

Fill the table in for each new material and source and file it with the lot documents.

Item	What you check	Pass condition	Where recorded
INCI name	On COA; matches CosIng	Same name on COA, SDS and file	Identity page
CAS number	Resolves in PubChem to the form ordered	Formula shows expected metal or counter-ion	Identity page
Molecular weight	PubChem value vs COA MS line	Expected and found agree	Identity page
Lot COA	Lot number on COA and vial	Lot-specific results, not a spec sheet	Lot folder
Chromatogram	Main peak, impurities, method header	Supplied and legible	Lot folder
SDS	16 sections; same manufacturer as COA	Product-specific	Lot folder
Manufacturer	Address; lot-code logic; public records	Lot found in a record library	Supplier page
Appearance, solubility, colour	Bench steps 1 to 3	Consistent with COA	Bench log
pH and UV-visible trace	Bench steps 4 and 5	Recorded; consistent with earlier lots	Bench log
Independent HPLC and MS	Bench step 6	Agrees with supplier COA	Lot folder

What to document in your own raw-material file

A raw-material file is what you hand to a safety assessor, an auditor or a colleague who takes over. For a peptide it should contain:

1. Identity page. INCI name, common name, CAS number for the exact form, PubChem CID, formula and molecular weight with their source, and a note on any second CAS number and why you rejected it.
2. Supplier page. Seller, manufacturer, site address, whether they are the same company, how the lot code is built and where public records are.
3. Lot folder, one per lot. COA, chromatogram, mass spectrum, SDS, date received, condition on receipt, retest date and any independent laboratory report.
4. Bench log. The six observations above with dates, photographs and the retained-sample location.
5. Decision. Accepted for trials, accepted for scale-up, or rejected, with the reason and the name of the person who decided.

Keep the file with your formulation records so a batch can be traced to its lot. The retest date is when the file needs a new entry: a fresh certificate or your own re-test of the retained sample.

Red flags that should stop a purchase

None of these proves a material is bad. Each means the seller has not shown you that it is good.

• No lot number on the COA, or one that is not on the vial.
• A round purity figure with no method. "Ninety-nine percent" with no column, detector, wavelength or chromatogram is a sales line, not a result.
• A GMP claim with nothing behind it. The letters printed on a certificate or a web page without a certificate number, an issuing body or an audit date are a claim to check, not a fact. Ask for the certificate and confirm it with the body that issued it.
• Inconsistent CAS numbers between website, COA and SDS, or a number that resolves in PubChem to a different form.
• No SDS, or one for a different product, for a solution rather than a powder, or naming a manufacturer that does not match the COA.
• Documents that will not survive a question: a seller who cannot explain their own lot code, who sends a chromatogram with the header cropped off, or who changes the manufacturer's name between two emails.
• Room-temperature shipping of a material whose own COA says 2–8 °C.

The regulatory boundary

Everything above is about identity and quality. It does not settle whether a peptide may be used in a cosmetic in a given market, at a given level, with a given claim. That decision belongs to the brand that places the finished product on the market, with its safety assessor, in each jurisdiction. A supplier's COA, SDS and database entries are inputs to that decision, not a market authorisation. What a supplier can properly provide is identity and purity documentation for the lot, a safety data sheet for the powder and a manufacturer you can name. Verify those, file them, and make the regulatory decision yourself.

Maintained by Pepti, a Guangzhou peptide manufacturer. Batch records referenced on this site are published at peptioem.com/coa. Last reviewed 2026-10-19.