"Third-party tested" may be the most common phrase in the research peptide market. It appears on product pages, banners and packaging, usually with no further detail. Because it costs nothing to print, it tells you very little on its own.
This guide sets out what the phrase should mean, what a genuine independent test looks like on paper, and a short routine for checking any supplier's claim, including ours.
What "third party" actually means
In testing, the first party is the maker, the second party is the buyer, and the third party is an independent laboratory with no stake in whether the material passes. The point of third-party testing is simple: the organization reporting the numbers has nothing to gain from the numbers looking good.
That only works if three things are true:
- The laboratory is genuinely independent of the supplier and the manufacturer.
- The laboratory is identifiable, so its independence and competence can be checked.
- The report is tied to the specific material you bought, meaning the lot in your vial.
If any one of these is missing, "third-party tested" becomes a claim you have to take on trust, which defeats the purpose.
The five questions to ask
1. Which laboratory ran the test?
A real report names the laboratory, gives its address and shows who authorized the report. An unnamed "independent lab" can't be checked. If a supplier won't name the lab, count the claim as unverified.
2. Is the laboratory accredited, and for what?
The international standard for the competence of testing laboratories is ISO/IEC 17025. Accreditation to it is granted by an accreditation organization, for a defined scope of methods. It is not a general badge. A laboratory can be accredited for some tests and not others.
A laboratory that describes its own experience of ISO 17025 accreditation lists what the standard adds in practice: formal training plans and records, method development and validation procedures, measurement of method uncertainty, a defined calibration and maintenance program, document control, corrective and preventive action, audits, and regular review of proficiency testing (Honsa and McIntyre, Journal of AOAC International, 2003). Those are the controls that make a number trustworthy.
What to check: the accreditation certificate number, the accrediting organization, and whether the scope covers the methods on your report (for example HPLC purity or LC-MS identity).
3. Does the report match my lot?
The lot or batch number on the report should match the number printed on your vial exactly. A "representative" report, reused across batches, tells you about a batch someone tested once. It doesn't tell you about yours.
4. Does the report show the evidence?
A credible report includes the raw evidence behind the headline numbers: the HPLC chromatogram and the mass spectrum, with method details. A typed "99.3%" with no trace is a statement, not evidence. Our guide to HPLC vs mass spectrometry explains what each trace proves. Related reading: HPLC vs Mass Spectrometry: What Each Test on a Peptide COA Actually Proves.
5. Can I reach the report myself?
The strongest setups let anyone look up the report from the lot number, without emailing a sales address and without a login. A permanent, shareable link means a colleague or reviewer can see exactly the same document you did.
What independent testing is supposed to catch
It is worth knowing why these questions matter. Official control laboratories that buy and test peptide products from the open market have documented the kinds of problems that independent testing exists to catch.
Belgium's Scientific Institute of Public Health screened the ten falsified peptide products most often found on the Belgian market, bought from suspected illegal online sellers. They reported high variation in the amount of peptide per unit, purities as low as 5–75% for cysteine-containing peptides, and the toxic elements arsenic and lead (Janvier et al., Talanta, 2018; DOI: 10.1016/j.talanta.2018.06.023).
The same institute's control laboratory published a screening method that identifies 25 peptides by LC-MS/MS and quantifies them by UHPLC, validated to ISO 17025 requirements (Vanhee et al., Talanta, 2015; DOI: 10.1016/j.talanta.2015.04.022). That paper is a good model of what "tested" should mean: a named, accredited-standard method, with identity and quantity measured separately.
Independent does not mean complete
Even a genuine third-party report only covers the tests that were run. A typical research-peptide COA covers HPLC purity and LC-MS identity, and sometimes endotoxin. It usually does not cover:
- Net peptide content, meaning how much of the powder is actually peptide rather than water and counterions;
- Elemental impurities such as lead or arsenic, which need ICP-MS;
- Residual solvents from synthesis.
Reference-standard laboratories take a much broader view. A 2023 paper from the United States Pharmacopeial Convention and the UK medicines regulator describes assigning a value to a lyophilized peptide vial by combining data from multiple labs, using NMR, mass spectrometry, chromatography, HPLC and GC (McCarthy et al., Pharmaceutical Research, 2023; DOI: 10.1007/s11095-023-03493-1). No routine research COA will match that, and it doesn't have to. The practical lesson is to know which tests a report covers and which it leaves out, so you can plan your own confirmation for the gaps that matter to your work.
Third-party, second-party and in-house: how they compare
| In-house (first party) | Buyer-commissioned (second party) | Independent lab (third party) | |
|---|---|---|---|
| Who runs the test | The maker or seller | A lab hired by the buyer | A lab with no stake in the outcome |
| Main strength | Fast, frequent, cheap | Answers exactly the buyer's question | Independence from the seller |
| Main weakness | The tester gains if the lot passes | Costly, one buyer at a time | Only as good as the lab and the tests chosen |
| What to ask | Is a lab named at all? | Which lab, which methods? | Which lab, which scope, which lot? |
In-house testing isn't worthless. Good manufacturers test every lot internally. It just shouldn't be sold as "third-party." And a third-party label only has value if the report can be traced to a named lab and your lot.
Red flags
- "Third-party tested" with no laboratory name anywhere.
- A report with no lot number, or a lot number that doesn't match your vial.
- An accreditation logo with no certificate number, or a scope that doesn't include the methods shown.
- Numbers with no chromatogram or spectrum.
- Reports available "on request" only.
- The same PDF attached to every product or every batch.
- A test date years older than the lot.
None of these proves a problem. Each one is a reason to ask more questions before the material goes into an experiment.
A five-minute check
- Find the lot number on your vial.
- Find the report for that lot. Note the laboratory name and test date.
- Look the laboratory up. Confirm it exists, and if an accreditation is claimed, find the certificate and check the scope.
- Confirm the report shows a chromatogram and a spectrum, with measured values next to specifications.
- File the report with your lab notes so anyone reviewing your work can see what material you used.
For critical work, consider sending a sample to a contract laboratory of your own choosing. That is the most independent test there is.
How Seratide approaches it
Every Seratide vial carries a lot number, and each lot has a record on the Lot lookup page: look it up by lot number, no login, with a permanent link. Each record is laid out to show HPLC purity against specification, identity by LC-MS, endotoxin, and the testing laboratory and date.
To be plain about where things stand: the records on that page today are layout samples. They are clearly marked, show the format only, and carry placeholder values. Issued laboratory reports replace them as each lot is analyzed. We'd rather say that than let a sample page pass for a test. You can read who operates Seratide on our About page, or browse the research peptides shelf.
Sources
All sources below were opened and their PubMed abstracts read on 2026-09-29. Claims are limited to what the abstracts state.
- Honsa JD, McIntyre DA. ISO 17025: practical benefits of implementing a quality system. J AOAC Int. 2003;86(5):1038-44. PubMed: https://pubmed.ncbi.nlm.nih.gov/14632407/
- Janvier S, et al. Impurity profiling of the most frequently encountered falsified polypeptide drugs on the Belgian market. Talanta. 2018;188:795-807. PubMed: https://pubmed.ncbi.nlm.nih.gov/30029448/ · DOI: https://doi.org/10.1016/j.talanta.2018.06.023
- Vanhee C, et al. Analysis of illegal peptide biopharmaceuticals frequently encountered by controlling agencies. Talanta. 2015;142:1-10. PubMed: https://pubmed.ncbi.nlm.nih.gov/26003685/ · DOI: https://doi.org/10.1016/j.talanta.2015.04.022
- McCarthy D, et al. Reference Standards to Support Quality of Synthetic Peptide Therapeutics. Pharm Res. 2023;40(6):1317-1328. PubMed: https://pubmed.ncbi.nlm.nih.gov/36949371/ · DOI: https://doi.org/10.1007/s11095-023-03493-1
For laboratory research use only.