A Melanotan II certificate of analysis is a test report for one lot. Read it in order. Check the lot number against the vial, then the test date. Next, check identity by mass near 1024.2 and that the C-terminal amide is intact. Last, check purity by RP-HPLC with the chromatogram, net peptide content, water, and the lab that issued it.
- Melanotan II is C50H69N15O9, average mass near 1024.2, PubChem CID 92432.
- Losing the terminal amide gives C50H68N14O10, which is exactly PT-141's formula.
- The two compounds differ by about one dalton and one ordinary hydrolysis.
- A rounded mass, or the words identity confirmed, cannot tell them apart.
- The same mass also confirms the lactam ring: an uncyclised chain is 18 heavier.
- Tryptophan gives real absorbance at 280 nm as a second detection wavelength.
What does a Melanotan II certificate actually certify?
A lab tech pulls one sample from a lot, runs the tests and writes down the results with the date. The certificate works like a receipt for that visit: it tells you about that one sample, not every vial ever made.
It records what a named laboratory measured on a sample drawn from one lot, on one date, by named methods. It is evidence about that sample rather than a warranty about the vial on your bench.
A specification sheet lists limits the product is supposed to meet, carries no lot number and no results, and describes an intention. A certificate carries both because it describes an event, and a page without a lot number on its face is the first kind whatever its heading says.
For this compound there is a further reason to want the observed mass printed as a number, and it is the most interesting fact on this page.
- Lot number on the report against the lot number on the vial
- Identity: observed mass near 1024.2, with a decimal place
- One dalton higher is a different catalog product, not an impurity
- Lactam ring confirmed: an uncyclised chain is about 18 heavier
- Purity at 214 nm, with 280 nm available thanks to the tryptophan
- Net peptide content, counterion and water by Karl Fischer
- Accession number confirmed at the issuing laboratory
What mass should the identity result show?
Melanotan II is a cyclic heptapeptide, molecular formula C50H69N15O9 with an average mass near 1024.2, cataloged as PubChem CID 92432.
The ring is a lactam bridge, formed between an amine and an acid, and the chain terminates in an amide rather than a free carboxylic acid.
That terminal amide is where the interesting chemistry lives. Losing it turns this molecule into a different compound, and not a hypothetical one: the result is another product carried in this same catalog.
What happens if the terminal amide is lost?
The molecule becomes PT-141. This is worth stating precisely because it is checkable from the formulas rather than asserted.
Melanotan II is C50H69N15O9. Replacing the terminal amide with a hydroxyl removes an NH and adds an O, giving C50H68N14O10, which is exactly the formula of PT-141, average mass near 1025.2.
So the two compounds differ by about one dalton, and the transformation from one to the other is a single ordinary hydrolysis. A vial of Melanotan II that has lost its terminal amide contains a different catalog product, and nothing about the powder announces the change.
Why does that make the printed mass matter so much?
Because one dalton is the entire distinction, and only a number reveals it. A certificate reading 1024 is describing Melanotan II. One reading 1025 is describing something else.
A certificate that says identity confirmed, or that reports a mass rounded to the nearest ten, cannot distinguish between the two at all. Neither can a purity figure, because the two compounds are similar enough that a routine gradient may not resolve them.
This is the sharpest example in the catalog of why these guides keep asking for the observed figure. Elsewhere the argument is general. Here, one digit changes which product you own.
It also changes what a supplier query should ask. Rather than asking whether the material is pure, ask what mass was observed and to how many decimal places it was reported. A laboratory that measured this compound properly will have the figure to hand, and a laboratory that rounded to the nearest whole number never distinguished the two products in the first place.
Is the lactam ring a separate question?
Yes, and it is answered by the same measurement. Forming the lactam bridge releases a molecule of water, so a linear precursor that never cyclised weighs about 18 more than the finished peptide.
Eighteen daltons is an unmissable difference on a 1,024-dalton molecule, far larger than the one-dalton amide question.
So the identity mass is doing three jobs at once here: confirming the sequence, confirming the ring closed, and confirming the terminal amide survived. Three structural facts, one number, and none of them visible if the certificate offers a verdict instead.
Worth noticing how differently the two structural questions behave. The ring failure is enormous and obvious; the amide failure is a single unit and decides which product you hold. Larger is not the same as more consequential, and this compound demonstrates that as clearly as anything in the catalog.
How do you read the certificate field by field?
Lot number first, against the vial. Then dates, where a test date should follow the fill date and a print date carries no analytical meaning.
Then identity by mass, stated as a number with at least one decimal place. Purity by reversed-phase HPLC with the chromatogram attached. Related substances, including the deamidated form. Net peptide content. Counterion. Water. Appearance last.
Each result needs its method beside it. Purity by area percent, by net peptide content and by amino acid analysis are three different numbers for one vial, and they do not agree with each other.
What does the purity figure leave out?
Anything that does not absorb at the detection wavelength or does not elute, and specifically anything the separation did not separate.
Peptides are read at 214 nanometres, which responds to the peptide bond. Melanotan II also contains tryptophan, giving it real absorbance at 280 nanometres, so a second wavelength is available.
The limitation that matters here is resolution rather than detection. The deamidated form differs by one dalton and a small change in charge, and whether a gradient separates the two is a property of the method rather than something guaranteed by it.
What is net peptide content, and why does it change the price?
A synthetic peptide ships as a salt carrying a counterion from purification, plus water absorbed because lyophilized peptide is hygroscopic.
The consequence is arithmetic. A vial labeled 10 milligrams may hold 10 milligrams of powder of which a real fraction is salt and water. Net peptide content of 80 percent means 8 milligrams of peptide, and two suppliers quoting the same price for the same nominal size are not selling the same amount.
Ask which basis the label uses. The cost per milligram comparison ranks the catalog on one basis so two quotes can be compared honestly.
What do the water and counterion fields tell you?
Water is measured by Karl Fischer titration, which is specific to water. Loss on drying reports everything volatile and reads high when residual solvent is present, so the two are not interchangeable.
Counterion identity is worth reading. Trifluoroacetate is the usual residue of preparative HPLC; acetate requires an extra exchange step. Melanotan II carries a lysine, so there is a positive charge for a counterion to pair with.
Both feed the net content arithmetic and explain most of the gap between a high area purity and a lower net peptide figure, which readers frequently mistake for a supplier contradicting itself.
What does the certificate not cover?
Everything after the sample was drawn. Storage temperature, light, how long the vial has been open and how it has been handled are all outside it.
The amide is the specific thing that changes afterwards. Hydrolysis of that group continues after release, driven by moisture, so a lot correct at test can carry a meaningful proportion of the deamidated compound months later.
Moisture ingress also quietly makes the net content figure optimistic, because the powder weighs more per unit of peptide than it did at test.
How do you verify the document is genuine?
Confirm the report at the issuing laboratory rather than with the seller. An independent laboratory issues each certificate against an accession number that resolves on its own site. If the number resolves to a different product, a different lot, or nothing, the document does not describe your material.
Certificates with the verification key removed deserve particular suspicion, and this is not hypothetical in this market. A PDF is easy to edit; a third-party lookup is not.
Lot reports for material supplied here resolve through the certificate verification page, and the sizes carried appear on the Melanotan II product record.
What is the regulatory position?
There is no FDA-approved drug product containing Melanotan II and no United States pharmacopeial monograph defining what an acceptable batch is. The specification a lot is released against is the supplier's own.
That matters more than usual for a compound one dalton away from a different product, because no external standard defines how the two must be distinguished or what limit applies to the deamidated form.
Material described here is supplied for laboratory use only, and nothing in this guide describes use in a person or an animal.
FOR LABORATORY AND IN-VITRO RESEARCH USE ONLY. NOT FOR HUMAN OR ANIMAL CONSUMPTION. NOT FOR PERSONAL, MEDICAL, DIAGNOSTIC, THERAPEUTIC, OR RECREATIONAL USE.
What is Melanotan II studied for?
Published research on Melanotan II investigates the areas below, which is a different question from what Melanotan II will do for anyone, a claim about a living system that nothing on this site is sold for.
What it is. A man-made ring-shaped peptide seven building blocks long that switches on melanocortin receptors indiscriminately.
What the research looks at. It appears in melanocortin receptor research about binding and selectivity.
How it is thought to work. A ring-shaped relative of alpha-MSH that acts across several melanocortin receptor types rather than picking one. That lack of selectivity is its defining feature and the reason it is studied as a broad melanocortin activator.
What is not established. No approved drug product. Regulators in several countries have issued public warnings about unapproved products sold under this name. This record covers how it behaves at its receptors and does not describe use in a person.
The full record, including the certificate for the lot in stock, is on the Melanotan II product page.
Common questions
What molecular mass should a Melanotan II certificate show?
What happens if the terminal amide is lost?
Why does a rounded mass on the certificate matter?
How is the lactam ring confirmed?
Would the purity figure catch the deamidated form?
Published certificates for Melanotan II
Every figure below is read from a report the laboratory issued for that lot; each page carries the PDF and the lab's own verification link.
More documentation guides
Sources
- PubChem Compound Summary for CID 92432, Melanotan II. The openable record giving the molecular formula C50H69N15O9 and average mass near 1024.2, and showing the terminal amide whose loss is described above.
- PubChem Compound Summary for CID 9941379, Bremelanotide. The openable record for PT-141, whose formula C50H68N14O10 is exactly what Melanotan II becomes when the terminal amide is replaced by a hydroxyl.
- ICH Q2(R2), Validation of Analytical Procedures . Defines specificity, including that a method must distinguish the target from closely related substances, which here means a compound one dalton away.
- Finnrick independent verification portal. Third-party lookup used to confirm a certificate resolves to the lot it claims to describe, rather than confirming a document with the seller who supplied it.
