(ox'' i ben' zone).
» Oxybenzone contains not less than 97.0 percent and not more than 103.0 percent of C14H12O3, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
Solution: 10 µg per mL.
Absorptivities at 287 nm, calculated on the dried basis, do not differ by more than 3.0%.
Congealing temperature 651: not lower than 62.0.
Loss on drying 731 Dry it in vacuum at 40 for 2 hours: it loses not more than 2.0% of its weight.
Standard preparation Dissolve an accurately weighed quantity of USP Oxybenzone RS in methanol, and quantitatively dilute with methanol, if necessary, to obtain a solution having a known concentration of about 10 µg per mL.
Assay preparation Dissolve about 100 mg of Oxybenzone, accurately weighed, in methanol in a 100-mL volumetric flask, dilute with methanol to volume, and mix. Agitate gently, if necessary, to hasten solution. Pipet 1 mL of the solution so obtained into a second 100-mL volumetric flask, dilute with methanol to volume, and mix.
Procedure Concomitantly determine the absorbances of the Assay preparation and the Standard preparation in 1-cm cells at the wavelength of maximum absorbance at about 287 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C14H12O3 in the portion of Oxybenzone taken by the formula:
10C(AU / AS)in which C is the concentration, in µg per mL, of USP Oxybenzone RS in the Standard preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 4164Pharmacopeial Forum: Volume No. 27(3) Page 2572