A: Ultraviolet Absorption á197Uñ—

B: Place about 1g in a beaker,warm to melt the cream,add about 25mLof water,and mix:the solution responds to the tests for Acetate á191ñ.

Standard preparation— Dissolve an accurately weighed quantity of USP Mafenide Acetate RSin 0.01Nhydrochloric acid,and dilute quantitatively and stepwise with the same solvent to obtain a solution having a known concentration of about 200µg per mL.

Assay preparation— Transfer a quantity of Cream,equivalent to about 100mg of mafenide acetate and accurately weighed,to a 60-mLseparator,and add 20mLof chloroform to dissolve it.Add 20mLof water,shake for 2minutes,allow the layers to separate completely,and discard the lower,chloroform layer.Repeat this washing with two separate 20-mLportions of chloroform,and discard the chloroform washings.Filter the aqueous phase through a dry filter into a 100-mLvolumetric flask.Rinse the separator and the filter with water,passing all rinses through the filter,add water to volume,and mix.Centrifuge about 30mLof the Assay preparation,then pipet 20mLof the clear,supernatant into a 100-mLvolumetric flask,add 1mLof 1Nhydrochloric acid,add water to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at the wavelength of maximum absorbance at about 267nm,with a suitable spectrophotometer,using 0.01Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C7H10N2O2S·C2H4O2in the portion of Cream taken by the formula: in which Cis the concentration,in µg per mL,of USP Mafenide Acetate RSin the Standard preparation,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.