Free arachidonic acid is a transient, critical substrate for the biosynthesis of eicosanoid second messengers. Arachidonic acid oxidizes spontaneously on exposure to room air, yielding a complex mixture of fatty acid peroxides. Peroxide-free arachidonic acid is obtained after removal of the peroxides by silicic acid chromatography, followed by immediate addition of the antioxidant BHT (2,6-Di-tert-butyl-4-hydroxytoluene). Arachidonic acid is also available without BHT (Catalog No. 90010).