ABSTRACT
If ever a material seemed ill suited for use in analytical assays, it is endotoxin. As a standard it has been domesticated, but not entirely tamed; captured from the wild, grown up in captivity on rich media; chemically groomed (by solvent extraction), and trained to behave in a somewhat civilized manner in modern assays. But still it prances like a caged lion, back and forth, unable to escape its dual amphiphilic nature; unable to decide on the direction it should go in aqueous solution. The hydrophobic end would much rather aggregate with ends of its own kind or stick to the plastic or glass of a test tube or container in which it resides (or parenteral closure to which it has been applied for depyrogenation validation) rather than mingle with water. Furthermore, the biological activity of endotoxin derived from different bacteria run the gamut from apyrogenic to highly pyrogenic (the extremes in variability holds true for endotoxicity also). Indeed, laboratories select different endotoxins for different purposes (i.e., product testing standards versus depyrogenation validation applications) given varying empirical recovery experiences. This chapter seeks to provide an overview for endotoxin as both a parenteral contaminant and as a standard used in modern assays.
