Anthralin Cream
»Anthralin Cream is Anthralin in an aqueous (oil-in-water)or oily (water-in-oil)cream vehicle.Anthralin Cream labeled to contain more than 0.1percent of anthralin contains not less than 90.0percent and not more than 115.0percent of the labeled amount of C14H10O3;and Cream labeled to contain 0.1percent or less of anthralin contains not less than 90.0percent and not more than 130.0percent of the labeled amount of C14H10O3.
Packaging and storage— Preserve in tight containers,in a cool place.Protect from light.
Labeling— Label it to indicate whether the cream vehicle is aqueous or oily.
Assay— [NOTE—Use low-actinic glassware.]
Internal standard solution,Mobile phase,System suitability preparation,Solvent blank solution,and Chromatographic system— Proceed as directed in the Assayunder Anthralin.
Standard preparation— Dissolve an accurately weighed quantity of USP Anthralin RSin dichloromethane to obtain a solution having a known concentration of about 0.25mg per mL.Pipet 2mLof this solution and 2mLof Internal standard solutioninto a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Assay preparation— Accurately weigh approximately 5g of Cream into a tared 100-mLbeaker.Add about 20mLof dichloromethane and 10mLof glacial acetic acid,and stir to disperse the Cream.Transfer the contents of the beaker to a filter paper (Whatman No.4,or equivalent)with the aid of dichloromethane,and filter into a 100-mLvolumetric flask.Thoroughly wash the precipitate with dichloromethane,and allow the washings to drain into the flask.Dilute with dichloromethane to volume,and mix.Pipet a volume of this solution,equivalent to about 0.5mg of anthralin,and 2mLof Internal standard solutioninto a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Procedure— Proceed as directed in the Assayunder Anthralin.Calculate the quantity,in mg,of anthralin (C14H10O3)in the portion of Cream taken by the formula:
(200C/V)(RU/RS),
in which Cis the concentration,in mg per mL,of USP Anthralin RSin the Standard preparation;Vis the volume,in mL,of the filtrate taken for the Assay preparation;,and RUand RSare the response ratios of the anthralin peak to the o-nitroaniline peak 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 162
Phone Number:1-301-816-8389
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