2,2-Diphenyl-1-picrylhydrazyl is used as a sensitive colorimetric free radical scavenger. It serves as a general antioxidant detector. It is utilized to monitor chemical reactions involving radicals as well as a standard of the position and intensity of electron paramagnetic resonance signals. Further, it is employed in the quantitative determination of aliphatic and aromatic thiols by indirect spectroscopy and for photometric determination of tocopherol.