Medium: 0.01 N hydrochloric acid; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C15H14F3N3O4S2 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 271 nm on filtered portions of the solution under test, suitably diluted with water, if necessary, in comparison with a Standard solution having a known concentration of USP Bendroflumethiazide RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C15H14F3N3O4S2 is dissolved in 45 minutes.

Mobile phase— Dissolve 5.62 g of sodium chloride and 1.97 g of anhydrous sodium acetate in 1000 mL of water in a 2-liter volumetric flask. Add 4.0 mL of glacial acetic acid and 800 mL of methanol, dilute with water to volume, mix, filter, and degas.

Standard preparation— Dissolve an accurately weighed quantity of USP Bendroflumethiazide RS in methanol, and dilute quantitatively and stepwise with methanol to obtain a solution having a known concentration of about 50 µg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 5 mg of bendroflumethiazide, to a 100-mL volumetric flask, add about 70 mL of methanol, and sonicate for 15 minutes, with occasional shaking. Dilute with methanol to volume, mix, and centrifuge a portion of the solution for 15 minutes.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 270-nm detector and a 4.6-mm × 30-cm column that contains packing L11 maintained at a temperature of 35 ± 5. The flow rate is about 1.5 mL per minute. Chromatograph five replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 3.0%, and the tailing factor 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 response of the major peak. Calculate the quantity, in mg, of C15H14F3N3O4S2 in the portion of Tablets taken by the formula: in which C is the concentration, in µg per mL, of USP Bendroflumethiazide RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.