Third-Party vs In-House Peptide Testing: What to Look For

A peptide test result is only as useful as the lab behind it and the lot it covers. "Third-party tested" means a laboratory independent of the seller ran the analysis. "In-house" means the seller or manufacturer tested its own material. Both can be legitimate, but they answer different questions about trust.

In-house testing

Manufacturers routinely test their own peptides, usually with HPLC for purity and mass spectrometry for identity (JPT Peptide Technologies). In-house testing is fast and useful for quality control. Its limitation is independence: the party reporting the result is also the party selling the product.

Third-party testing

An independent lab receives a sample, runs its own analysis and issues its own report. A good third-party report names the lab, identifies the sample and lot, gives the test date and method, and shows the raw data, such as the HPLC chromatogram and the observed mass.

What lab accreditation tells you

Some testing labs are accredited to ISO/IEC 17025, the international standard for testing and calibration laboratories. It "specifies the general requirements for the competence, impartiality and consistent operation of laboratories," and accreditation means an independent body has assessed the lab against it (ANAB). Accreditation covers specific test methods, so check that the method used on a report falls within the lab's accredited scope.

How to check a report against your vial

1. Match the lot number on the report to the lot number on your vial.
2. Confirm the lab's name and the test date appear on the report.
3. Look for both a purity result (HPLC) and an identity result (mass spectrometry).
4. Where the lab issues a verification code or portal, use it to confirm the report is genuine.
5. Remember that a report covers only the tests it lists. Standard HPLC and MS don't measure sterility or endotoxin.

For a field-by-field walkthrough, see How to Read a Peptide COA. For how purity and identity are measured, see Peptide Purity Testing.

Zerilyx testing

Zerilyx publishes certificates by lot on the Certificates of Analysis page. Each certificate names the lab that issued it, and where the lab provides an access code it's shown so the result can be checked on the lab's portal. See Quality for how lots are verified.