Endotoxin Testing

Ensure that the water used as a solvent has an extremely low endotoxin level, and regularly monitor and maintain the water filtration system used for development of products. In manufacturing situations lacking access to such filtration systems, it is most cost efficient and safe to purchase water tested for endotoxin.

Prepare buffers in a clean environment using clean containers and filter them immediately after preparation to prevent microbial contamination.

Adjust the pH of the solution to fall within the 6.4 to 8 pH range, as the endotoxin assay functions best in this range.

High salt concentration (> 1M) can inhibit the endotoxin assay, so samples with high salt concentrations should be diluted.

Detergents can interfere with the detection of endotoxins, so buffer solutions with detergents should be diluted before testing.

Chelators like EDTA, EGTA or Citrate can inhibit the endotoxin assay, so dilution of samples with chelators is necessary.

Chaotropic agents like urea or guanidine chloride can alter endotoxin aggregates that result in inhibition of LAL activity, so appropriate dilutions are required.

High concentrations of organic solvents can dissolve lipid A, the lipid portion of endotoxins, leading to inhibition of the assay.

Impure sugars containing β-glucans can yield false-positive results, so use highly purified sugars.

Serum proteins such as Bovine Serum Albumin (BSA) or Human Serum Albumin (HSA) can affect endotoxin detection, so dilute samples containing serum albumin.

Nucleic acids and fatty acids can cause inaccurate results, so monitor and correct these parameters.