A: Infrared Absorption 197K.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds 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 USP Mafenide Related Compound A RS. in Mobile phase having a known concentration of about 25 µg per mL. [NOTE—USP Mafenide Related Compound A RS is 4-formylbenzenesulfonamide.]

Working standard solution— Pipet 10.0 mL of Concentrated standard solution into a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

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

Standard solution— Pipet 10.0 mL of Working standard solution into a 50-mL volumetric flask, dilute with Mobile phase to 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 mafenide related compound A 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 20 µL) of the Mobile phase, the Working standard solution, and the Test solution into the chromatograph, allowing the Test solution to 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 C is the concentration, in mg per mL, of USP Mafenide Related Compound A RS in the Working standard solution; ri is the peak response for each impurity obtained from the Test solution; and rS is the peak response of mafenide related compound A 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 0.5 mL of propionic acid in 100.0 mL of water.

Standard solution— Transfer about 50 mL of water to a 100-mL volumetric flask, insert a stopper, and weigh. Add 0.5 mL of 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 200 mg of mafenide acetate, to a 100-mL volumetric flask containing 200 mg of oxalic acid. Pipet 10.0 mL of Internal standard solution into the flask, dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)— 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 40 cm per second. The column temperature is programmed as follows. It is maintained at 150 for 11 minutes; then increased at a rate of 25 per minute to 240; maintained for 10 minutes; then decreased at a rate of 25 per minute to 150; and maintained for 1 minute 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 1 µL) of the Test solution and the Standard solution into the chromatograph, record the chromatograms, and measure the responses for 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 C is the concentration, in mg per mL, of acetic acid in the Standard solution; and RU and RS are the peak response ratios of acetic acid to propionic acid obtained from the Test solution and the Standard solution, respectively.

(Official January 1, 2007)

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

Mobile phase— Prepare a filtered and degassed mixture of Ion-pairing solution and acetonitrile (9:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Transfer about 25 mg of USP Mafenide Acetate RS, accurately weighed, to a 25-mL volumetric flask. Add about 12 mL of Mobile phase, and dissolve by sonication. Dilute with Mobile phase to 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 25 mg of mafenide acetate, to a 25-mL volumetric flask. Using sonication, dissolve in about 12 mL of Mobile phase. Dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)— 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 1.0 mL per 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 20 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Mafenide Acetate RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.