The ES Buffer is an endotoxin-specific buffer that is ideal for untreated LAL. Though all LAL reagents produced by FUJIFILM Wako LAL are endotoxin-specific, other commercially available LAL reagents are not. Without this buffer, tests can present a potential false positive when trying to determine the endotoxin concentration in the sample.

The ES Buffer works by adding a large amount of carboxymethylated curdlan (CMC) to LAL, thus preventing the activation of LAL by glucan. The presence of large amounts of glucan does not interfere with the quantitation of endotoxin. FUJIFILM Wako first made use of these findings by developing this endotoxin-specific buffer, which contains high concentrations of CMC. When the ES Buffer is used to reconstitute LAL, reagent becomes endotoxin-specific.