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C6H6O2 110.11

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.
USP Reference standards 11
USP Hydroquinone RS
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%.
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— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
(MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2589
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.