Effect of heat on endotoxin in plasma and in pyrogen-free water, as measured in the Limulus amoebocyte lysate assay

Four modes of heating endotoxin in plasma and two different times of heating endotoxin in pyrogen-free water were compared. There were no significant differences in standard curves after heating endotoxin in plasma at 100°C for 1 and for 10 min. However, the standard curve after heating for 10 min at 75°C had a significantly less steep slope, and after heating for 10 min at 56° C, it was completely flat. Heating of endotoxin in pyrogen-free water for 1 min also resulted in the flattening of the standard curve, which was even more pronounced after 10 min of heating.