Independent testing

    Third-Party Tested Peptides UK

    Compounds are sourced from vetted manufacturers, HPLC and mass spectrometry tested at the manufacturer (documentation not shipped with orders), with certificates published in the COA Library where available. Independent retesting is supported by the 14-day purity refund policy. This page explains how that verification works and where to read the results yourself.

    How Peptx verification works

    Supplier vetting through independent labs

    Compounds are sourced from vetted manufacturers, with suppliers vetted through independent lab testing. Suppliers whose material does not match its label are not stocked.

    HPLC and mass spectrometry at the manufacturer

    Material is HPLC and mass spectrometry tested at the manufacturer. That documentation is not shipped with orders; certificates are published in the COA Library where available.

    Independent retesting supported

    You are free to retest any batch you receive with an accredited laboratory of your choosing. Independent retesting is supported by the 14-day purity refund policy.

    14-day purity dispute window

    If you independently test a batch with an accredited laboratory and the result falls below its stated minimum purity, you can raise a dispute within 14 days of delivery with the test report and supporting documentation.

    Full terms are set out on the purity guarantee page.

    Browse the COA Library

    The COA Library holds our published certificates of analysis: measured content, purity as reported, batch references and, where the issuing laboratory provides one, a verification code you can check directly. Recent independent lab results are published there, alongside every test we have booked, listed before its result arrives.

    View the COA Library

    Reading a certificate of analysis

    Two analytical methods do most of the work on a peptide certificate, and they answer different questions. High-performance liquid chromatography separates the components of a sample and reports the proportion attributable to the main peak, which is where a purity percentage comes from. Mass spectrometry measures molecular mass, which is how identity is confirmed: a sample can be highly pure and still be the wrong molecule, so a purity figure on its own is incomplete without an identity check.

    When reading a certificate, check that the batch or lot reference on the document matches the label on the vial you received, that the issuing laboratory is named and independent of the manufacturer, that both purity and identity methods appear, and that the reported net peptide content is stated rather than only the gross fill weight. A certificate with no lot reference, no laboratory name or no date cannot be tied to the material in front of you.

    Longer explainers: HPLC vs mass spectrometry for peptide purity verification and how to check a certificate of analysis.

    UK Express

    Single vials, 24-hour dispatch.

    Some products are account-only — sign in to see the full range
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    Factory Direct

    Top sellers, factory direct.

    Volume pricing, 5 kits −5%, 10 kits −10%, auto-applied at checkout (Factory Direct).

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    Frequently asked questions

    What is a certificate of analysis?
    A certificate of analysis, or COA, is the analytical report issued for a specific production batch. It records the measured content and purity of the material, the analytical methods used, typically high-performance liquid chromatography and mass spectrometry, the batch or lot reference, and the laboratory that performed the work.
    What does third-party tested mean?
    It means the analysis was performed by a laboratory independent of the manufacturer and the seller. Every certificate Peptx publishes comes from an outside laboratory, suppliers are vetted through independent lab testing, and certificates are published in the COA Library where available.
    Who carries out the independent lab tests?
    Independent laboratories carry out the tests used in supplier vetting (published results so far come from Janoshik, Marfleet, BT Labs, Chromate and Analiza Białek, with further testing booked at Vanguard Laboratory), alongside the manufacturer's own HPLC and mass spectrometry documentation, which is not shipped with orders. You can also retest independently, supported by the 14-day purity refund policy.
    How do I verify a batch myself?
    Take a sample from the vial you received and send it to an independent laboratory of your choosing. The laboratory directory on our testing page lists accredited options across the United Kingdom, Europe and the United States. Where a certificate is published and carries a verification code, you can check it directly with the issuing laboratory using the code and link shown on the entry in the COA Library.