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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 Click to View Structure
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.
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Monograph Feiwen Mao, M.S.
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(SM32010) Monographs - Small Molecules 3
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USP35–NF30 Page 3451