How to read a peptide certificate of analysis

Every supplier in this trade will send you a certificate. Most of them are real documents describing a production run that finished a year ago and is not what is in your box. Knowing how to read one is less about spotting forgeries and more about knowing which numbers carry weight and which are decoration.

The four numbers that matter

Identity, by mass spectrometry. The report should state an observed molecular weight and a theoretical one, and they should match within about one dalton. This is the single most important line on the page. It answers "is this the compound on the label", which is a different question from "is it clean". A vial can be beautifully pure and be the wrong molecule.

Purity, by HPLC. Reported as a percentage of total peak area. Ninety-eight percent and up is the normal claim. The number alone tells you very little, because it depends entirely on how the baseline was integrated and where the operator chose to stop counting. What you want is the chromatogram itself, printed on the certificate, so you can see whether the main peak is sharp and whether there are shoulders sitting next to it.

Net peptide content. How much of the powder is actually peptide, with the remainder being bound water, acetate or trifluoroacetate counter-ions, and residual salts from synthesis. This is routinely 75 to 90 percent, and it is the number that decides what a milligram on the label is worth. A supplier who reports purity but not net content is showing you the flattering half.

Water content, by Karl Fischer. Lyophilised peptides are hygroscopic. High residual moisture shortens shelf life and shifts the real mass of peptide in the vial. Under five percent is unremarkable. Over ten and the material has been handled or stored badly.

What means nothing

A date with no lot number attached to it. A certificate describes one batch. If the document does not carry a lot or batch identifier that also appears on the carton you received, the two are not connected and nobody is claiming they are.

A company letterhead on a certificate the company issued about its own product. In-house QC is not independent testing. It may be perfectly honest and it is still the manufacturer marking its own homework.

A watermark that has been removed. Independent labs watermark reports because the report number is checkable. Janoshik, the lab most commonly used in this market, lets anyone verify a report number against their records. A certificate with the lab's identity stripped out is a document whose only purpose is to stop you checking it.

Appearance, solubility and pH lines. They are real tests and they are trivially passed. Nothing about a white powder dissolving tells you what the powder is.

The gap nobody in this trade talks about

Reference certificates and shipped batches come apart almost immediately. A factory runs a synthesis, tests it, publishes the report, and then runs that compound another forty times over the next two years without retesting each run. The certificate stays in circulation because it is the only paper anyone has.

This is not necessarily fraud. The starting materials and the process usually are the same. But "usually the same" is a claim about a process, not a measurement of your batch, and any supplier who tells you the certificate was run on the vials in your box is almost certainly guessing.

What to do instead

Buy one box, send one vial to a lab, and pay the sixty to ninety dollars. You will get identity, purity and net content on the material you actually hold, with a report number under your own name that you can publish to your own customers. That document is worth more to your brand than any supplier's paperwork, because it is the only one your buyers cannot accuse you of having been handed.

At Halden we host the manufacturer's reference reports and label them as exactly that. We do not claim they describe your lot. We would rather pay for your test than argue about ours, so the cost of your first independent test is credited against your next order up to one hundred dollars, and a batch that misses spec is refunded in full.

Ask for the chromatogram, not the summary. Ask which lot the report covers. If the answer is vague, you have learned something useful about the supplier at no cost.