All tools used for endotoxin detection must be free from endotoxin and β-glucan. Dry-heating at 250 °C for more than 30 minutes is required to inactivate endotoxin. The use of glassware treated by dry heat sterilization is recommended. Avoid metal tools, since even a small amount of eluted metal ions (e.g. Fe, Al, Ga, Cr) may affect testing. When using disposable plastic tools (not guaranteed by its manufacturer for use for Endotoxin test purposes), check if they satisfy the requirements: 1) Not contaminated by endotoxin; 2) No adsorption of endotoxin; and 3) No eluted substance; in comparison with glassware.
Use the appropriate type of standard endotoxin based on the testing purpose.
Precautions are required against the potential impact (reaction interferences) of samples on endotoxin tests.
These interferences are categorized into the following two types:
The effect of samples can be judged by a test referred to as the test for interference factors by Pharmacopoeias: namely, it is conducted by measuring a sample which has been spiked with a known amount of endotoxin and obtaining the recovery of the spiked endotoxin. If the recovery is within the 50 to 200 % range, then the sample is determined as not influential, in other words, the measured endotoxin concentration is correct. If any sample influence is found, it can be reduced by diluting the sample solution for measurement. However, dilution of the sample solution raises the endotoxin concentration value obtained through the conversion to the concentration of the original solution (pre-dilution solution). The possible dilution multiple (maximum valid dilution) is determined based on the desired endotoxin concentration to be detected and the detection sensitivity of the LAL reagent to be used (refer to the Bacterial Endotoxins Test by the Pharmacopoeia for details of the reaction interference factors and maximum valid dilution).