The use of a quantitative assay in endotoxin testing.

By utilizing Limulus Amebocyte Lysate (LAL) and a chromogenic peptide substrate it is now possible to determine endotoxin concentrations quantitatively down to 10 EU/L (1 pg/mL) in a two stage assay. The optimal reaction conditions found for the two stages of the method, the endotoxin reaction with LAL and the measurement of the activation with the chromogenic substrate, are briefly described. The properties of the final kit reagents have also been investigated and the results are included. Finally, the usefulness of the present method is demonstrated by results obtained from testing therapeutical products as well as clinical plasmas. Some factors which may be critical in the performance of the assay are discussed.