What endotoxin is
Endotoxins are lipopolysaccharides from the outer membrane of gram-negative bacteria. They can be introduced during synthesis, purification, handling or packaging, and they survive many processes that kill bacteria. A sample can be 99% pure by HPLC and still carry endotoxin, because the two tests measure different things.
Why it matters in research
In cell-based and other in-vitro work, endotoxin contamination can trigger strong responses on its own and confound results. That is why laboratories screen reagents for it, and why an endotoxin result on a report is useful information about a research material.
How USP <85> works
USP <85> is the United States Pharmacopeia’s bacterial endotoxins test. It uses Limulus amebocyte lysate (LAL), which reacts to endotoxin. Labs run the sample against standards, often in replicate, and report either a measured value in endotoxin units (EU) or a pass against a stated limit.
How to read the result
- Method: the report should name the method, such as USP <85>.
- Replicates: running the test more than once (for example 2 replicates) makes the result more reliable.
- Pass or value: a pass means the sample met the limit the lab tested against. A numeric result is in EU, often per mg or per mL.
- Lot: as with every test, it only applies to the lot on the report.
A pass does not mean “zero endotoxin”. It means the result was within the limit tested. Read the report for the exact wording.
Which Arctic reports include it
Arctic’s October 2026 reports from Freedom Diagnostics include an endotoxin result: a pass on USP <85> with 2 replicates, alongside LC-MS identity and HPLC-UV purity. They cover Tesamorelin 10MG (lot TS-2502B), BPC-157 10MG (lot BP-2501A), GHK-Cu 100MG (lot GHK-2502B), KLOW 80MG (lot GW-2501A) and one more lot listed in the report library.
Check ours yourself. Every current report is public, with the lot number and a link to the lab’s own verification page.
Questions
What is endotoxin testing?
An endotoxin test measures bacterial endotoxins (lipopolysaccharides from gram-negative bacteria) in a sample. It is separate from purity: a sample can be very pure by HPLC and still contain endotoxin.
What is USP <85>?
USP <85> is the United States Pharmacopeia bacterial endotoxins test. It uses Limulus amebocyte lysate (LAL) to detect endotoxin and reports a value in endotoxin units (EU) or a pass against a limit.
Does an endotoxin pass mean zero endotoxin?
No. A pass means the result was within the limit the lab tested against. Read the report's exact wording and limit.
Why does endotoxin matter for research peptides?
Endotoxin can provoke strong responses in cell-based and other in-vitro systems on its own, which can confound results. That is why labs screen research materials for it.
Do Arctic's reports include endotoxin testing?
Arctic's October 2026 Freedom Diagnostics reports include an endotoxin pass on USP <85> with 2 replicates. Each report in the library at arcticlabsupply.com/coas lists the tests that were run.