Silver Sulfadiazine Cream
»Silver Sulfadiazine Cream contains not less than 90.0percent and not more than 110.0percent of the labeled amount of C10H9AgN4O2S.
Packaging and storage— Preserve in collapsible tubes or in tight,light-resistant containers.
Identification— Dissolve about 35mg of USP Sulfadiazine RSin 4mLof ammonium hydroxide,add 16mLof methanol,and mix to obtain the Standard solution.Transfer a quantity of Cream,equivalent to about 50mg of silver sulfadiazine,to a stoppered,50-mLconical flask,add 4mLof ammonium hydroxide,and mix until a smooth paste has been obtained.Add 16mLof methanol,shake for 5minutes,and filter to obtain the test solution:the test solution so obtained responds to the Thin-layer Chromatographic Identification Test á201ñ,a mixture of chloroform,methanol,and ammonium hydroxide (7:4:1)being used as the developing solvent.[NOTE—Prepare the developing solvent by first mixing the chloroform and methanol,and then adding the ammonium hydroxide.]
Microbial limits á61ñ— It meets the requirements of the tests for absence of Staphylococcus aureus,Pseudomonas aeruginosa,Salmonella species,and Escherichia coliand the total count does not exceed 23cfu per g.It meets also the requirements for Total Combined Molds and Yeasts Count,fewer than 10cfu per g being found.
Minimum fill á755ñ: meets the requirements.
pHá791ñ: between 4.0and 7.0,determined in the supernatant obtained from a 1in 20mixture of the Cream in water.
Assay—
Mobile phase and Diluting solution—Proceed as directed in the Assayunder Silver Sulfadiazine.
Internal standard solution— Dissolve an accurately weighed quantity of sulfamerazine in Diluting solution,and dilute quantitatively,and stepwise if necessary,with Diluting solutionto obtain a solution having a known concentration of about 2mg per mL.
Standard stock solution— Dissolve an accurately weighed quantity of USP Silver Sulfadiazine RSin Diluting solutionto obtain a solution having a known concentration of about 1mg per mL.
Standard preparation 1— Pipet 10.0mLof the Standard stock solutioninto a 50-mLtest tube.Add 20mLof alcohol and 5.0mLof the Internal standard solution,and mix.
Standard preparation 2— Pipet 2.0mLof Standard preparation 1into a 50-mLtest tube.Add 40mLof Mobile phase,and mix.
Assay preparation— Transfer an accurately weighed portion of Cream,equivalent to about 10mg of silver sulfadiazine,to a 50-mLround-bottom centrifuge tube.Add about 30mLof methanol,tightly seal the tube with a cap containing an inert liner,and mix,using a vortex mixer,for about 15seconds.Centrifuge for 15minutes.Aspirate,and discard the methanol.[NOTE—Care should be taken to avoid aspirating any of the residue.]Transfer 5.0mLof the Internal standard solutioninto the tube,and add 20mLof alcohol.Replace the cap,and mix.Heat in a water bath at 60,with periodic mixing,for 15minutes to melt and disperse the Cream.While the mixture is still hot,transfer 10.0mLof Diluting solutionto the tube,mix,and cool to room temperature.Transfer 2.0mLof this solution to another tube,add 40mLof Mobile phase,mix,and filter.
Chromatographic system— Proceed as directed in the Assayunder Silver Sulfadiazine.Chromatograph replicate injections of Standard preparation 2,and record the peak responses as directed for Procedure:the resolution,R,between sulfadiazine and sulfamerazine is not less than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 10µL)of Standard preparation 2and the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of silver sulfadiazine in the portion of Cream taken by the formula:
10C(RU/RS),
in which Cis the concentration,in mg per mL,of USP Silver Sulfadiazine RSin the Standard stock solution;and RUand RSare the relative peak response ratios obtained from the Assay preparationand Standard preparation 2,respectively.
Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1822
Phone Number:1-301-816-8394