A plain-language guide to what endotoxins are, which laboratory samples can be tested, and how we test them.
Endotoxins are lipopolysaccharides (LPS), molecules that make up part of the outer membrane of Gram-negative bacteria (a large group of common bacteria with a double outer layer, named for how they look under a standard lab stain). They are released when bacteria die or divide, so they can be present even when no living bacteria remain.
They are remarkably heat-stable. Endotoxins survive many common sterilization steps, including standard autoclaving. That means a product can be sterile (no living organisms) and still contain endotoxin. Sterility testing and endotoxin testing answer different questions.
You can't see, smell, or taste them. The only way to know whether endotoxin is present is to test for it.
Because endotoxins come from common bacteria, they can turn up in water and in anything made with or exposed to water. We test aqueous (water-based) and water-soluble laboratory samples using LAL gel-clot and kinetic chromogenic methods:
Everyday drinking and household water types, tested as laboratory samples.
Examples: municipal tap water, bottled spring water, store-bought distilled water.
Why it matters: Shows the baseline endotoxin level of water before it is used to prepare research materials.
Water that has been specially cleaned for lab work.
Examples: deionized (DI) water, reverse-osmosis (RO) water, ultrapure water from a lab purification system.
Why it matters: Water goes into almost every lab workflow, so contaminated water can quietly affect everything made with it.
Sterile water with a small amount of benzyl alcohol added, used to dissolve research materials.
Examples: multi-use vials of bacteriostatic water from any supplier or lot.
Why it matters: Confirms the liquid used for dissolving isn't itself adding endotoxin.
Short chains of amino acids made for laboratory research.
Examples: lyophilized (freeze-dried) peptide powders and reconstituted peptide solutions (powder that has been dissolved in liquid).
Why it matters: Verifies a research material is free of endotoxin that could skew experimental results.
Liquids labs use to keep pH steady or dissolve samples.
Examples: phosphate-buffered saline (PBS), Tris buffer, sterile water for reconstitution.
Why it matters: Endotoxin in a reagent carries over into every experiment that uses it.
The nutrient liquids labs use to grow cells.
Examples: DMEM, RPMI-1640, fetal bovine serum (FBS) supplements.
Why it matters: Cultured cells can react to endotoxin, which may change how they grow and respond, and skew data.
Powders that dissolve in water before use.
Examples: amino acids, sugars like dextrose or mannitol, salts like sodium chloride, peptide powders before reconstitution.
Why it matters: Screening ingredients before use helps keep contamination out of finished research preparations.
We rinse the inside of an item with endotoxin-free water and test the rinse.
Examples: empty vials, stoppers, lab containers, pipette tips, tubing, glassware.
Why it matters: Shows whether a surface is adding endotoxin to whatever it touches.
Not sure if your sample is compatible? Some materials interfere with LAL tests; we'll confirm compatibility before quoting.
The sample is mixed with LAL reagent and incubated. If endotoxin is present at or above the reagent's sensitivity level, the liquid thickens into a firm gel, like a tiny set gelatin. It's a simple, well-established method that gives a pass/fail or approximate-amount result.
LAL reacts with endotoxin to release a yellow color from a color-producing ingredient (a "chromogenic substrate"). The instrument measures how quickly the color develops and calculates an exact amount by comparing it to known endotoxin standards. We run this method on the Charles River Endosafe® PTS™ cartridge system.
Some samples can suppress or enhance the LAL reaction. To check, a portion of each sample is spiked with a known amount of endotoxin and the recovery is measured. Recovery within the USP <85> acceptance range (50–200%) shows that the sample isn't interfering and that the result can be trusted. Where needed, samples are diluted to overcome interference.
BioVis assigns a unique lot number to every sample we receive; it appears on your Certificate of Analysis and is used to look up and verify your results. Anyone with the lot number and verification code can confirm a result on our Verify Results page.
The sender's name and mailing address on the package are verified against the PO.
Packages are opened in a dedicated receiving area, separate from the testing room. Contents are inspected and photographed to document their condition on arrival.
Each sample's outer surfaces are sprayed with 70% isopropyl alcohol before it enters the clean room.
Every sample receives a tamper-evident seal bearing its unique BioVis lot number.
Samples are stored until they reach the temperature required by their test method.
Each test is performed to the method's precise measured requirements for the most accurate results possible. If a confirmation retest is needed, it's performed at no additional cost.
Results are reviewed and posted online under your lot number, typically within 24–48 hours.
Leftover material: Most tests leave extra sample material. Any remaining material is disposed of safely in accordance with standard laboratory waste practices.
All BioVis testing is analytical and for research use only. Research peptides are not approved by the U.S. Food and Drug Administration (FDA) for human or animal use. Our results report measured endotoxin levels only — they do not establish that any product is safe, effective, or suitable for consumption, and should never be used as a basis for human or animal use. Educational content only; not regulatory, medical, or clinical advice.
