Endotoxin Testing and Why It Matters in the Lab

A compound can be very pure and still carry bacterial endotoxins. That is why many researchers look for an endotoxin report alongside the purity report.

What endotoxins are

Endotoxins are fragments of the outer membrane of certain bacteria. They are extremely stable, survive many common sterilisation methods, and can interfere with cell-based experiments even in tiny amounts.

How they are measured

The most widely used method is the LAL (Limulus Amebocyte Lysate) assay. Results are reported in endotoxin units (EU), usually per milligram or per vial. Lower is better, and the report will often show the result against a stated limit.

Why it is a separate test

HPLC measures chemical purity. It cannot see endotoxins, because they are present in quantities far below what chromatography detects. A sample can show 99%+ purity on HPLC and still fail an endotoxin limit.

What to look for

• A report from an independent laboratory.
• A sample ID that matches your batch number.
• A clear result with units and the limit it was tested against.

Where an endotoxin report is available for a batch, it is listed next to the purity report on our Lab Results page. Batches still in testing are marked as such until the results are published.

For laboratory research use only. Not for human or animal consumption.