Endotoxin will adhere to glass surfaces, but this can be counteracted with proper vortexing to ensure that the solution you aliquot into your reaction tubes or microplate has the proper EU/ml concentration. As our package inserts state, the CSE vial should be vigorously vortexed for 15 minutes prior to making dilutions. This should be repeated each time you use the vial, not just after reconstitution. Each CSE dilution should be vortexed for at least one minute prior to use. It is also a good idea to vortex the CSE dilutions for a few seconds immediately before use.