2,2-diphenyl-1-picrylhydrazyl

DPPH is a common abbreviation for the organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable free radical molecules. DPPH has two major applications, both in laboratory research: one is a monitor of chemical reactions involving radicals, most notably it is a common antioxidant assay, and another is a standard of the position and intensity of electron paramagnetic resonance signals.

DPPH has several crystalline forms which differ by the lattice symmetry and melting point. The commercial powder is a mixture of phases which melts at ~130 °C. DPPH-I (m.p. 106 °C) is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is triclinic.

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.

2,2-diphenyl-1-picrylhydrazyl is a free radical, which shows hydrogen acceptor ability towards antioxidants. It has a strong absorbance at 517 nm. When the radical is lost in exchange for a proton, the absorbance at 517 nm decreases proportionately, resulting in a color change from purple to yellow. Hence, it is commonly used in DPPH assay for measuring the antioxidant activity of different natural samples such as wine, fruits, herbal tea etc.

This picrylhydrazyl derivative, also known as DPPH free radical, presents as a black crystalline powder. Store in a refrigerator - this substance is heat sensitive. 1,1-Diphenyl-2-picrylhydrazyl Free Radical is incompatible with oxidizing agents, strong bases and halogens. This chemical is harmful if swallowed. It may cause allergy or asthma symptoms or breathing difficulties if inhaled and an allergic reaction on the skin.

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