Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 60 minutes.

Procedure— [NOTE—Conduct the analysis of the specimen promptly after the specimen aliquot is withdrawn from the vessel, to minimize hydrolysis.] Determine the amount of C8H8Cl3N3O4S2 dissolved, employing the procedure set forth in the Assay, making any necessary volumetric adjustments.

Tolerances— Not less than 65% (Q) of the labeled amount of C8H8Cl3N3O4S2 is dissolved in 60 minutes.

(Official January 1, 2007)

Mobile phase and Chromatographic system—Prepare as directed in the Assay under Trichlormethiazide.

Acidic methanol— Add 2.8 mL of sulfuric acid to 100 mL of water, mix, and cool. Dilute with methanol to 1000 mL, and mix.

Internal standard solution— Transfer about 20 mg of methylparaben to a 200-mL volumetric flask, add Acidic methanol to volume, and mix.

Standard preparation— Transfer about 20 mg of USP Trichlormethiazide RS, accurately weighed, to a 50-mL volumetric flask, add Acidic methanol to volume, and mix. Transfer 5.0 mL of this solution to a centrifuge tube, add 5.0 mL of Internal standard solution, and mix to obtain a solution having a known concentration of about 0.2 mg of USP Trichlormethiazide RS per mL.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to 2 mg of trichlormethiazide, to a centrifuge tube. Add 5.0 mL of Acidic methanol and 5.0 mL of Internal standard solution, and mix to disperse the powder. Insert the stopper in the tube, rotate by mechanical means for 20 minutes, and centrifuge to obtain a clear supernatant.

Procedure— Separately inject equal volumes (5 µL to 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. The relative retention times are about 0.58 for trichlormethiazide and 1.0 for methylparaben. Calculate the quantity, in mg, of C8H8Cl3N3O4S2 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Trichlormethiazide RS in the Standard preparation, and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.