U.S. PHARMACOPEIA

Search USP29  
Hydroquinone
Click to View Image
C6H6O2 110.11

1,4-Benzenediol.
Hydroquinone [123-31-9].
» Hydroquinone contains not less than 99.0 percent and not more than 100.5 percent of C6H6O2, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight, light-resistant containers.
Identification—
B: Prepare a solution of it in methanol containing approximately 1 mg per mL, and prepare a similar solution of USP Hydroquinone RS. Apply 5 µL of each solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of equal volumes of methanol and chloroform until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Heat on a hot plate or under a lamp until spots appear: the RF value of the principal spot obtained from the solution under test corresponds to that obtained from the Standard solution.
C: A 1 in 40,000 solution in methanol exhibits an absorbance maximum at 293 ± 2 nm.
Melting range 741: between 172 and 174.
Water, Method I 921: not more than 0.5%.
Residue on ignition 281: not more than 0.5%.
Organic volatile impurities, Method I 467: meets the requirements.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Dissolve about 250 mg of Hydroquinone, accurately weighed, in a mixture of 100 mL of water and 10 mL of 0.1 N sulfuric acid, add 3 drops of diphenylamine TS, and titrate with 0.1 N ceric sulfate VS until a red-violet endpoint is reached. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N ceric sulfate is equivalent to 5.506 mg of C6H6O2.
Auxiliary Information— Staff Liaison : Feiwen Mao, M.S., Senior Scientific Associate
Expert Committee : (MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
USP29–NF24 Page 1082
Phone Number : 1-301-816-8320