Testing & Verification
Endotoxin Testing
Overview
Endotoxin testing detects and quantifies a specific class of contaminant associated with certain bacteria. It is a contamination measurement, entirely separate from the identity, purity, or quantity of the intended substance.
What an endotoxin is
Endotoxins are heat-stable molecules — lipopolysaccharides — that form part of the outer membrane of Gram-negative bacteria and are released particularly when those cells break down. Because they can persist even after the bacteria themselves are gone, a material can be free of viable organisms and still carry endotoxin. Endotoxin testing is therefore a distinct question from whether living microbes are present.
What the test measures
Endotoxin testing detects the presence of bacterial endotoxin in a sample and estimates its level. It is contamination-focused: it characterises one specific category of unwanted material, not the intended substance. The result speaks only to endotoxin — not to identity, not to purity, and not to how much of the intended molecule is present.
Why a purity figure does not cover it
A chromatographic purity percentage describes the proportion of the detected signal that is the main component under that method. Endotoxin is measured by its own dedicated approach and is not what a purity method is designed to reveal. A high purity figure says nothing about endotoxin status, which is why the two are reported separately.
What this test can and cannot establish
What it can establish
- Whether bacterial endotoxin is detected, and an estimate of its level
- Information about one specific contamination category
- A result independent of, and not implied by, a purity figure
What it cannot establish
- Identity, purity, or quantity of the intended substance
- Sterility — the absence of viable organisms is a separate test
- Any suitability, safety, or appropriateness for any use
Key terminology
- Endotoxin
- A heat-stable lipopolysaccharide from the outer membrane of Gram-negative bacteria.
- Lipopolysaccharide
- The class of molecule that bacterial endotoxins belong to.
- Contamination testing
- Testing for substances other than the intended material.