Reading a certificate of analysis

Many shops publish a certificate of analysis, usually shortened to CoA, for the products they list. Peptilyze does not collect, check or rate these documents. This guide is general reading help: what a CoA normally contains and which details make one easier to judge.

What a CoA is

A CoA is a document that reports the results of tests on a batch of a product. It can come from the manufacturer, from the seller, or from a separate laboratory. Who produced it matters, and it is the first thing to find out.

What it usually lists

• Product name and strength as the seller describes it.
• Batch or lot number that ties the report to a specific production run.
• Test date and often a manufacturing date.
• Method. For peptides, two methods turn up most often. HPLC reports a purity figure as a percentage of the signal. Mass spectrometry reports the measured molecular mass, which is compared with the expected one to confirm identity.
• Result for each test, usually next to a specification or acceptance limit.
• Laboratory name and contact details.
• Signature or stamp of a named person, and sometimes the chromatogram or spectrum itself.

Details that make a CoA easier to rely on

• The batch number on the report matches the one on the vial or the order.
• The date is recent and fits the batch.
• The lab is named, can be looked up, and has no financial tie to the seller.
• The raw data (chromatogram, spectrum) is included, not only a summary line.
• The report states the method and the acceptance limit, not just “pass”.
• Different batches have different reports.

Details that make one harder to rely on

• No batch number, or one that never changes.
• No test date.
• No named laboratory, or a logo with no way to contact the lab.
• One generic PDF shown for every product or every batch.
• A purity figure with no method, or a figure that is the same to the decimal across many products.
• Edited screenshots, blurred sections or a file you cannot open yourself.

A CoA is still a claim

Unless an independent laboratory confirms it, a CoA is the seller’s statement about its own product. You can sometimes ask the named lab whether it issued a report with that number. You can also ask the seller for the report of the exact batch you are ordering.

Be careful with what a number means. A purity percentage describes how much of the measured signal belongs to the main substance. It does not say how much is in the vial, what the rest is, or whether anything is suitable for a given purpose. Peptilyze draws no such conclusion from a CoA and neither should a price table.

Questions worth asking a seller

• Which laboratory produced the report, and can I contact it?
• Is this report for the batch I will receive?
• Which methods were used, and what are the acceptance limits?
• Do you test every batch, or only the first one?

What Peptilyze does with this

Nothing about CoAs enters our tables or rankings. A shop being cheap or expensive tells you nothing about its documents, and a shop that shows a CoA is not ranked above one that does not. The shop pages say plainly that lab reports are among the things we do not check.