Third-party testing means an analysis commissioned from a laboratory with no commercial stake in the result. It is the only mechanism that checks a supplier's documentation rather than accepting it, and it is the reason the phrase carries weight — which is also why it is so often used loosely.
What makes testing genuinely independent
Testing arranged and paid for by the supplier, from a laboratory the supplier selected, is not the same thing — even when the laboratory itself is entirely competent. The independence being claimed is independence of the party with an interest in the outcome.
- The laboratory is named, and can be contacted without going through the supplier.
- The laboratory has no ownership relationship with the supplier.
- The report is issued to the commissioning party, and identifies who commissioned it.
- The sample's origin is recorded, so the report is about a known material.
Choosing a laboratory
| Check | Why it matters |
|---|---|
| Accreditation and its scope | ISO/IEC 17025 is granted for named methods. Verify the entry on the accreditation body's public register, and confirm the scope covers the analysis you are ordering. |
| Peptide-specific experience | General analytical capability does not imply familiarity with peptide-specific behaviour and impurity profiles. |
| Methods actually offered | Purity, intact mass, sequence confirmation, net peptide content and endotoxin are separate services. Confirm each one you need. |
| Reporting format | Ask whether raw chromatograms and spectra are included, or only a summary table. |
| Sample requirements | Minimum quantity and acceptable condition vary. Ordering the wrong amount wastes a shipment. |
| Turnaround and cost | Publicly stated by some laboratories, quote-only at others. |
What to order
Order by the question you need answered rather than by package name. The common combinations are narrow.
| Question | Analysis to request |
|---|---|
| Is this the compound it claims to be? | Intact mass by LC-MS; tandem MS if the mass alone would be ambiguous |
| How much of the detected material is that compound? | RP-HPLC purity, with chromatogram and full method |
| How much of the vial is actually peptide? | Amino acid analysis for net peptide content |
| Is bacterial endotoxin present above a limit? | Bacterial endotoxin test (LAL) |
| Is it sterile? | Sterility testing — a separate test that nothing else implies |
| What is the water and counterion content? | Karl Fischer titration and ion chromatography |
Chain of custody
A result is only as meaningful as the record of what was tested. Before shipping, record the lot number, the supplier and order reference, the receipt date, and the condition of the container. Photograph the intact, labelled container. Ship according to the laboratory's stated conditions.
Testing a sample the laboratory received from the supplier, rather than from you, reintroduces exactly the dependency the exercise was meant to remove.
Reading the report you paid for
- Confirm the report identifies your lot number, not a generic sample identifier.
- Compare the observed mass against the expected mass for the named sequence, and check the charge states shown.
- Read the purity figure together with its method and detection wavelength; a number without them is not comparable to anything.
- Note explicitly what was not tested. A report is silent on every analysis it did not perform.
- Where your result diverges from the supplier's, the useful next step is to ask them for the same lot's raw chromatogram rather than to re-argue the summary figures.
Sources
- ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories
- FDA — Pyrogen and Endotoxins Testing: Questions and Answers
- ANAB — accredited laboratory directoryPublic register for verifying a US laboratory's ISO/IEC 17025 accreditation and scope.
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