Ultrafiltration as a means to eliminate inhibition of the Limulus Amoebocyte Lysate (LAL) assay

Inhibition of the Limulus Amoebocyte Lysate (LAL) assay for the detection of endotoxin is often a problem when testing parenteral solutions with actual concentrations of chemical substances. Seven samples of sterile, pyrogen-free solutions widely used in Norwegian hospitals, with inhibiting effect on the LAL test, were spiked with endotoxin, and ultrafiltered with different volumes of diluent. For six of the seven samples the inhibition was reduced or eliminated.