Limulus Amebocyte Lysate (LAL) is an aqueous extract of blood cells (amoebocytes) from the horseshoe crab, Limulus polyphemus. LAL reacts with bacterial endotoxin or lipopolysaccharide (LPS), which is a membrane component of Gram negative bacteria as well as with 1,3-β-D-glucan which is typical as component of fungi cell walls. This reaction is the basis of the LAL test, which is the used for the detection and quantification of bacterial endotoxins and 1,3-β-D-glucans.

There are three methods for LAL test: Gel Clot assay, Turbidimetric assay and Chromogenic assay. The last two can be categorized as photometric methods due to the fact that a photometer is necessary for the analysis.

• Gel Clot assay: The simplest LAL test. The form of a clot indicates endotoxin presence in a sample. The method is performed in small appropriate test tubes and a simple manual procedure (tube reversal) reveals the result. Maximum sensitivity is as low as 0.03 ΕU/mL. Associates of Cape Cod offers a variety of products with a set of sensitivities 0.03 ΕU/mL, 0.06 ΕU/mL, 0.125 ΕU/mL and 0.25 ΕU/mL.


• Chromogenic assay (Kinetic/Endpoint): LAL reagent is fitted with a synthetic substrate (para Nitroaniline) which turns to yellow due to endotoxin presence in a sample. The method is performed with a photometer at 405 nm. It is a quantative method and the maximum sensitivity is 0.001 EU/mL. Associates of Cape Cod offers two products for this method: Chromo-LAL (kinetic Chromogenic assay with max sensitivity 0,005 EU/ml with an incubating plate reader) and Pyrochrome (kinetic/endpoint assay with max sensitivity 0,001 EU/ml with a Pyros Kinetix Flex).


• Turbidimetric assay (Kinetic): It is a method similar to Gel Clot, while the procedure that leads to Gel Clot is monitored as it is performed through turbidity measurements at 660 nm. The maximum sensitivity for this method can be as low as 0.001 EU/mL if a Pyros Kinetix Flex instrument is used with the reagent of Associates of Cape Cod: Pyrotell-T.


• Control Standard Endotoxin: Endotoxin vials which can be used as standard for LAL test.