The hydroperoxy HPLC mixture contains several of the principle LO-derived hydroperoxides of arachidonic acid and linoleic acid supplied in ethanol. This HPLC mixture contains 5 µg of the following fatty acid hydroperoxides: 5(S)-HpETE, 12(S)-HpETE, 15(S)-HpETE, 9(S)-HpODE, and 13(S)- HpODE.