A: Ultraviolet Absorption 197U—

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.

for oral solution packaged in single-unit containers: meets the requirements.

for oral solution packaged in multiple-unit containers: meets the requirements.

note—Throughout the following procedures, protect test or assay specimens, the USP Reference Standards, and solutions containing them, by conducting the procedures without delay, under subdued light, or using low-actinic glassware.

Mobile phase, System suitability solution, and Chromatographic system— Proceed as directed in the Assay.

Standard solution— Dissolve an accurately weighed quantity of USP Furosemide Related Compound B RS in Diluting solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of about 15.0 µg per mL.

Test solution— Transfer an accurately measured portion of Oral Solution, equivalent to about 10 mg of furosemide, to a 10-mL volumetric flask, dissolve in and dilute with Diluting solution to volume, and mix.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks: the peak response of furosemide related compound B obtained from the Test solution is not greater than the corresponding peak response obtained from the Standard solution.

Mobile phase— Prepare a filtered and degassed mixture of water, acetonitrile, and glacial acetic acid (165:35:2). Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluting solution— Prepare a mixture consisting of water, acetonitrile, and glacial acetic acid (22:22:1).

System suitability solution— Dissolve suitable quantities of USP Furosemide RS, USP Furosemide Related Compound A RS, and USP Furosemide Related Compound B RS in Diluting solution to obtain a solution containing about 0.1 mg of each per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Furosemide RS in Diluting solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of about 1 mg per mL.

Assay preparation— Transfer an accurately measured portion of Oral Solution, equivalent to about 10 mg of furosemide, to a 10-mL volumetric flask, dissolve in and dilute with Diluting solution to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L10. The flow rate is about 2 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.2 for furosemide related compound B, 1.0 for furosemide, and 1.1 for furosemide related compound A; the resolution, R, between furosemide and furosemide related compound A is not less than 1.5; and the tailing factor for the furosemide peak is not more than 1.5. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of furosemide (C12H11ClN2O5S) in the portion of Oral Solution taken by the formula: in which C is the concentration, in mg per mL, of USP Furosemide RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.