Monobenzone
;)
Phenol,4-(phenylmethoxy)-.
p-(Benzyloxy)phenol [103-16-2].
»Monobenzone,dried at 105
for 3hours,contains not less than 98.0percent and not more than 102.0percent of C13H12O2.
for 3hours,contains not less than 98.0percent and not more than 102.0percent of C13H12O2.
Packaging and storage—
Preserve in tight,light-resistant containers,and avoid exposure to temperatures above 30.
.
Identification—
A:
Infrared Absorption á197Kñ.
B:
Ultraviolet Absorption á197Uñ—
Solution:
10µg per mL.
Medium:
methanol.
Absorptivities at 292nm,calculated on the dried basis,do not differ by more than 3.0%.
C:
Transfer about 500mg of Monobenzone,previously dried,to a 150-mLflask fitted with a reflux condenser,employing a suitable glass joint.Add 5mLof pyridine and 3mLof acetic anhydride,reflux for 10minutes,and cool.Add 100mLof water and 6mLof acetone to the flask,and insert a stopper.Cool the contents of the flask in a refrigerator for 1hour,collect the precipitate in a sintered-glass crucible,and wash the precipitate with water until no odor of pyridine remains.Dry the precipitate for 16hours in a vacuum desiccator over phosphorus pentoxide.The monobenzone acetate so obtained melts between 110and 113when determined as directed for Class I(see Melting Range or Temperature á741ñ).
and 113when determined as directed for Class I(see Melting Range or Temperature á741ñ).
Loss on drying á731ñ—
Dry it at 105for 3hours:it loses not more than 1.0%of its weight.
for 3hours:it loses not more than 1.0%of its weight.
Residue on ignition á281ñ:
not more than 0.5%.
Organic volatile impurities,Method Vá467ñ:
meets the requirements.
Solvent:
dimethyl sulfoxide.
Assay—
Standard preparation—
Dissolve an accurately weighed quantity of USP Monobenzone RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 40µg per mL.
Assay preparation—
Transfer about 100mg of Monobenzone,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.Pipet 4mLof this solution into a 100-mLvolumetric flask,dilute with methanol to volume,and mix.
Procedure—
With a suitable spectrophotometer,using methanol as a blank,concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the wavelength of maximum absorbance at about 292nm.Calculate the quantity,in mg,of C13H12O2in the portion of Monobenzone taken by the formula:
2500C(AU/AS),
in which Cis the concentration,in mg per mL,of USP Monobenzone RSin the Standard preparation;and AUand ASare the absorbances obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information—
Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 1311
Phone Number:1-301-816-8389