Recovery of endotoxin preparations from the surface of glass capillary tubes

The gel-clot method of the Limulus Amebocyte Lysate (LAL) test was used to determine the recovery efficiency of four different endotoxin preparations from Type I glass capillary tubes. Each capillary tube was charged with 10,000 endotoxin units (EU) and vacuum-dried at 50 degrees C. Average recovery for the Whittaker M.A. Bioproducts Control Standard Endotoxin (CSE), which contained fillers, was 90% (80-100%), for the Difco Laboratories and Associates of Cape Cod endotoxins 47% (40-80% and 20-100%, respectively), and for the rough lipopolysaccharide 70% (40-100%). The presence of fillers appears to increase the percentage of endotoxin recovered and decrease the inconsistency in recovery results. The overall recovery rates for the pure endotoxin formulations were higher and slightly more consistent than those reported in previous studies.