A:Infrared Absorption á197Kñ.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Ion-pairing solution and Mobile phase— Proceed as directed in the Assay.

Concentrated standard solution— Prepare a solution of USP4-Formylbenzenesulfonamide RSin Mobile phasehaving a known concentration of about 25µg per mL.

Working standard solution— Pipet 10.0mLof Concentrated standard solutioninto a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

System suitability solution— Transfer about 10mg of USP Mafenide Acetate RS,accurately weighed,to a 10-mLvolumetric flask,and dissolve by sonication in about 2mLof Mobile phase.Pipet 4.0mLof Concentrated standard solutioninto the same flask,dilute with Mobile phaseto volume,and mix.

Standard solution— Pipet 10.0mLof Working standard solutioninto a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Test solution— Use the Assay preparation.

Chromatographic system— Prepare as directed in the Assay.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between mafenide acetate and 4-formylbenzenesulfonamide is not less than 3.0;and the tailing factor is not more than 2.0.Chromatograph the Working standard solution,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2.0%.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:adjust the integration parameters so that the response is between 5%and 15%of full-scale deflection.

Procedure— Separately inject equal volumes (about 20µL)of the Mobile phase,the Working standard solution,and the Test solutioninto the chromatograph,allowing the Test solutionto elute for a period of not less than three times the retention time of mafenide acetate;record the chromatograms,and measure the responses for the major peaks,disregarding the peaks corresponding to those obtained from the Mobile phase.Calculate the percentage of each impurity in the portion of the constituted Topical Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP4-Formylbenzenesulfonamide RSin the Working standard solution;riis the peak response for each impurity obtained from the Test solution;and rSis the peak response of 4-formylbenzenesulfonamide obtained from the Working standard solution:not more than 0.5%of any individual impurity is found;and not more than 1.0%of total impurities is found.

Internal standard solution— Dissolve 0.5mLof propionic acid in 100.0mLof water.

Standard solution— Transfer about 50mLof water to a 100-mLvolumetric flask,insert a stopper,and weigh.Add 0.5mLof glacial acetic acid to the flask,insert the stopper,weigh,and calculate,by difference,the amount of acetic acid added.Dilute with water to volume,and mix.

Test solution— Constitute the Topical Solution as directed in the labeling.Transfer an accurately measured volume of the constituted Topical Solution,equivalent to about 200mg of mafenide acetate,to a 100-mLvolumetric flask containing 200mg of oxalic acid.Pipet 10.0mLof Internal standard solutioninto the flask,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 0.25-mm ×60-m fused-silica capillary column coated with a 0.5-µm layer of acid-deactivated phase G35.The carrier gas is helium,flowing at a rate of 40cm per second.The column temperature is programmed as follows.It is maintained at 150for 11minutes;then increased at a rate of 25per minute to 240;maintained for 10minutes;then decreased at a rate of 25per minute to 150;and maintained for 1minute prior to the next injection.The detector and the injection port temperatures are maintained at 250.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the resolution,R,between acetic acid and propionic acid is not less than 3.0;and the relative standard deviation of the peak response ratios for replicate injections is not more than 6.0%.

Procedure— Separately inject equal volumes (about 1µL)of the Test solutionand the Standard solutioninto the chromatograph,record the chromatograms,and measure the responses of all the peaks.Calculate the quantity,in mg,of acetic acid in the portion of the constituted Topical Solution taken by the formula: in which Cis the concentration,in mg per mL,of acetic acid in the Standard solution;and RUand RSare the peak response ratios of acetic acid to propionic acid obtained from the Test solutionand the Standard solution,respectively.

Ion-pairing solution— Dissolve 6.8g of monobasic potassium phosphate and 1.0g of sodium 1-hexanesulfonate in about 800mLof water.Adjust with phosphoric acid to a pHof 2.5,dilute to 1000mL,and mix.

Mobile phase— Prepare a filtered and degassed mixture of Ion-pairing solutionand acetonitrile (9:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Transfer about 25mg of USP Mafenide Acetate RS,accurately weighed,to a 25-mLvolumetric flask.Add about 12mLof Mobile phase,and dissolve by sonication.Dilute with Mobile phaseto volume,and mix.

Assay preparation— Constitute the Topical Solution as directed in the labeling.Transfer an accurately measured volume of the constituted Topical Solution,equivalent to about 25mg of mafenide acetate,to a 25-mLvolumetric flask.Using sonication,dissolve in about 12mLof Mobile phase.Dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 267-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 1.0mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of mafenide acetate (C7H10N2O2S·C2H4O2)in the portion of the constituted Topical Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Mafenide Acetate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.