How to read a certificate of analysis

A certificate of analysis, usually shortened to COA, is the closest thing a research peptide has to a passport. It is issued by a testing laboratory for one production lot and records what the laboratory found. Read properly, it takes less than a minute to check. Read carelessly, it can suggest more than it actually says.

Start with the lot number

Every certificate belongs to one lot. The first check is whether the lot number on the certificate matches the number printed on your vial label. If it does not, the certificate is about a different batch, however similar the product name. In the UKPeps certificate library you can enter the lot number from the label and go straight to the matching row.

Check the vial size

A laboratory tests a sample from a specific fill: 5 mg vials, 10 mg vials and so on. A certificate issued for a 5 mg vial documents the substance and the lot, but not the quantity in a 10 mg vial. Where our certificates were issued for a different vial size from the one sold on a page, the product page says so in a highlighted note.

Look at the method before the number

A purity figure only means something next to the method that produced it. High-performance liquid chromatography (HPLC) separates the components of a sample and reports the main peak as a share of all detected peaks. Mass spectrometry confirms that the molecule has the expected mass, which supports its identity but is not a purity figure. Other screening methods report results in their own way. The two laboratories in our library use different methods, so we show the method beside every result and never average across them.

Specification versus measured value

A supplier's specification, such as "purity at least 98%", is a requirement. The certificate shows what was actually measured for one lot, for example 99.51%. A product page that quotes only the specification tells you nothing about a particular vial. A useful page links to the measured value.

What a certificate does not cover

Storage after testing: the certificate reflects the sample on the day of analysis, not how the vial was kept afterwards.
Other lots: one good certificate does not vouch for the next batch.
Suitability for any use outside the laboratory: a certificate is an analytical record, not an approval.

Excipients and superseded lots

Some lots contain an excipient such as mannitol, added before freeze-drying to give the powder structure. The certificate states this, and our library marks the row "with mannitol". When a formulation changes, the earlier certificate stays available for vials still in circulation and is marked "superseded".

Who the certificate names

Certificates in the UKPeps library name SwissPeps as the client, because the analyses are commissioned once for the whole SPEPS Group by the company that operates both shops. The lots are the same ones UKPeps dispatches from UK stock.

All certificates are open to read, without an account, in the certificate library.

Sources

Mant CT et al. HPLC analysis and purification of peptides. Methods Mol Biol, 2007. PubMed 18604941 · doi:10.1007/978-1-59745-430-8_1
A methods chapter on HPLC, including reversed-phase modes, for analysing and purifying peptides.
Sharma N et al. Synthetic pharmaceutical peptides characterization by chromatography principles and method development. J Sep Sci, 2022. PubMed 35460196 · doi:10.1002/jssc.202101034
A review of chromatographic principles and method development for characterising synthetic peptides.
Lian Z et al. Characterization of Synthetic Peptide Therapeutics Using Liquid Chromatography-Mass Spectrometry: Challenges, Solutions, Pitfalls, and Future Perspectives. J Am Soc Mass Spectrom, 2021. PubMed 34110145 · doi:10.1021/jasms.0c00479
A review of LC-MS approaches for characterising synthetic peptides.
Guthals A et al. Peptide identification by tandem mass spectrometry with alternate fragmentation modes. Mol Cell Proteomics, 2012. PubMed 22595789 · doi:10.1074/mcp.R112.018556
A review of peptide identification by tandem mass spectrometry using different fragmentation modes.

Published laboratory and preclinical research, cited for scientific context only. It is not evidence of safety or effect in people.