Storing research peptides: temperature, light and shelf life

Every reputable peptide supplier will tell you their products are tested. Far fewer will show you the test.

A certificate of analysis is that test, written down. It is a document produced by a laboratory stating what was in a specific batch, how they measured it, and when. If you know how to read one, it is the single most useful thing on a product page.

Most people glance at the purity number and stop. There is more worth knowing.

What a COA actually is

A sample is taken from a production batch and sent to a laboratory. The lab runs a set of analyses on it and issues a certificate recording what they found.

The important word is batch. A COA describes one specific production run, not the product in general. A certificate from eighteen months ago says nothing about the batch in your hand.

The sections, and what they mean

Product name and batch number. The identifier that ties the certificate to physical stock. This is the one to check first, because it is the one that fails most often: the number on the certificate should match the number printed on what you received.

Date of analysis. When the testing was done, which also tells you how old the batch is.

Appearance. Usually a line like “white lyophilised powder” or “clear colourless solution”. Trivial on its own, but it is a basic identity check — a copper peptide solution that is described as colourless rather than blue would be a problem.

Identification by mass spectrometry. This answers whether the compound is what it claims to be. Mass spectrometry measures molecular weight, and every peptide has a known theoretical weight based on its amino acid sequence. The certificate shows the theoretical figure and the one observed. They should be close, usually within a fraction of a unit.

This section matters more than purity. A 99% pure sample of the wrong compound is still the wrong compound.

Purity by HPLC. High-performance liquid chromatography separates a sample into its components and measures the proportion of each. The purity figure is the percentage of the sample that is the target compound.

For research peptides, 98% or above is the normal standard. Below 95% is worth questioning. The remaining percentage is not necessarily anything sinister — it is typically related peptide fragments left over from synthesis — but you should be able to see what it is.

A good certificate includes the actual chromatogram, the graph of peaks from the HPLC run, not just the final number.

Water content. Freeze-dried peptides hold some residual moisture. Usually reported by Karl Fischer titration, typically under 10%.

Acetate content. Many peptides are supplied as acetate salts, and this reports how much is acetate rather than peptide. Relevant because it affects how much of the stated weight is the compound itself.

Bacterial endotoxins and sterility. Not always present, and more common on products intended for higher-grade applications.

Four things worth checking

1. Does the batch number on the certificate match the batch number you received? If the supplier publishes one generic COA for all stock regardless of batch, that is not batch testing.
2. Who issued it? An in-house certificate from the manufacturer is not the same as one from an independent accredited laboratory. Both have value, but they are not equivalent.
3. Is the chromatogram included? A purity figure with no underlying data behind it is a claim rather than a result.
4. How old is it? A current batch should have a recent certificate.

Why we publish them

Nuewell publishes the certificate for every batch directly on the product page, before purchase, rather than supplying it on request afterwards. The batch number printed on your pen matches the certificate you can read now.

That is the point of a COA. It is only useful if you can see it before you decide.

Supplied strictly for laboratory research purposes. Not a medicine, not a dietary supplement, and not for human or veterinary consumption.