Factors affecting the sensitivity of Limulus lysate.

Limulus lysate clots when mixed with picogram quantities of endotoxins. The sensitivity of the lysate was improved 100-fold by the removal of an inhibitor and addition of divalent cations. The methods developed in this investigation eliminated much of the seasonable variability of the lysate, improved the heat stability after lyophilization, and made it possible to use the lysate with saline solutions.