The word "azide" refers to a chemical compound that typically contains three nitrogen atoms bonded together. It is a very reactive and potentially explosive substance often used in explosives, detergents, and pharmaceuticals. Full definition
The cells were then washed once with FACS buffer I, once with FACS buffer II (0.01 % sodium azide in PBS), and fixed with 1 % formaldehyde in PBS. (biomedical-engineering-online.biomedcentral.com)
Unlike Abdulmutallab's bomb, the new device contained lead azide, an explosive often used as a detonator. (scientificamerican.com)
The cells were enzymatically removed from the culture dish with Tryple ™ Select (Invitrogen) for 15 min at 37 °C, resuspended in 1 ml FACS buffer I (2 % FBS, 0.01 % sodium azide in PBS), and counted with Neubauer cell counter chambers. (biomedical-engineering-online.biomedcentral.com)