Assay—
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 C
14H
12O
3 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.
;)
651
:
not lower than 62.0
.