Endotoxin
Definition
Lipopolysaccharide from the outer membrane of Gram-negative bacteria. It survives ordinary sterilisation and is not removed by filtration alone, and it provokes a febrile inflammatory response, which is why it is assayed separately from sterility.
In more detail
Endotoxins are lipopolysaccharide fragments from the outer membrane of Gram-negative bacteria. They are heat-stable and survive conditions that kill the organism, so sterile material is not automatically low in endotoxin: the two are separate tests answering separate questions.
The measurement is biological rather than chemical, using an amoebocyte lysate assay or a recombinant equivalent, and results are reported in endotoxin units per vial or per milligram against a stated limit.
Terms used in this definition
Other entries this definition refers to.
Where this term comes up
Entries whose definition mentions Endotoxin.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
LAL Test (Limulus Amebocyte Lysate)
The endotoxin assay, which uses a clotting cascade from horseshoe crab blood that endotoxin triggers. A result on a certificate is a quantity against a limit, not a yes or no.
Sterility Testing
Incubation of a sample in growth media to confirm no viable microorganism is present. Sterility is a property of a validated process and its container and is independent of chemical purity: a very pure material can be non-sterile and often is.
Sterility
The absence of viable microorganisms in a preparation. It is conferred by a process and preserved by a closure, so it is lost the moment either is compromised and nothing about the appearance of a vial reports that.
Assay
Any procedure that measures whether something is present, how much of it there is, or how active it is. Analytical assays report composition; functional assays report activity, and a material can pass one and fail the other.
Quality Control (QC)
The testing a batch passes through before release, typically identity by mass spectrometry, purity by HPLC, content and, where relevant, water, sterility and endotoxin. QC is the set of tests; the certificate is the report of their results.
Degradation Product
A compound formed as a peptide breaks down, through oxidation, deamidation, hydrolysis or aggregation. Certificates report these as impurity peaks, and their pattern says more about how a batch was handled than the headline purity figure does.
Reference Standard
A well-characterised sample run alongside an unknown so that retention time and response can be compared against something known. Without one, a chromatogram shows separation but supports no identification.
Batch Number
The identifier tying a quantity of material to the records of its manufacture and testing. It is the only thing linking a vial in hand to a certificate on a screen, which is why a certificate whose batch number does not appear on the label proves nothing about that vial.
