(dye ox'' i ben' zone).
» Dioxybenzone contains not less than 97.0 percent and not more than 103.0 percent of C14H12O4, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 10 µg per mL.
Absorptivities at 286 nm, calculated on the dried basis, do not differ by more than 3.0%.
Congealing temperature 651: not lower than 68.0.
Loss on drying 731 Dry it in vacuum at 40 for 2 hours: it loses not more than 2.0% of its weight.
Assay Dissolve about 100 mg of Dioxybenzone, accurately weighed, in toluene in a 100-mL volumetric flask, dilute with toluene to volume, and mix. Pipet 1 mL of this solution into a second 100-mL volumetric flask, add methanol to volume, and mix. Similarly, prepare a Standard solution of USP Dioxybenzone RS, accurately weighed, having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 325 nm, with a suitable spectrophotometer, using a 1 in 100 solution of toluene in methanol as the blank. Calculate the quantity, in mg, of C14H12O4 in the Dioxybenzone taken by the formula:
10C(AU / AS)in which C is the concentration, in µg per mL, of USP Dioxybenzone RS in the Standard solution, and AU and AS are the absorbances of the solution of Dioxybenzone and the Standard solution, respectively.
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USP35NF30 Page 2930