A: Ultraviolet Absorption 197U— Transfer a portion of the contents of the Capsules, equivalent to about 0.1 g of triamterene, to a 250-mL volumetric flask. Add 100 mL of methoxyethanol, shake until dissolved, dilute with water to volume, and mix. Transfer 5 mL of this solution to a 200-mL volumetric flask, add 5 mL of formic acid, and dilute with water to volume. Prepare a solution of USP Triamterene RS in the manner described above to obtain a Standard solution with a final concentration of about 10 µg per mL. Determine the UV spectrum from 280 nm to 420 nm.

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.

TEST 1—

TEST 2— If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.

(Official January 1, 2007)

Buffer solution and Mobile phase— Proceed as directed in the Assay under Triamterene and Hydrochlorothiazide Tablets.

Standard preparation— Transfer about 50 mg of USP Triamterene RS, accurately weighed, to a 100-mL volumetric flask. Add 10 mL of acetonitrile, 10 mL of water, and 5 mL of glacial acetic acid, sonicating for 3 minutes after each addition. Cool to room temperature, dilute with water to volume, and mix.

Assay preparation— Remove, as completely as possible, the contents of 20 Capsules, combine the contents, and transfer an accurately weighed portion of powder, equivalent to about that which is in one dosage unit, to a 100-mL volumetric flask (Flask 1). To a separate 100-mL volumetric flask, add all 20 capsule shells (Flask 2). For each flask, add 10 mL of acetonitrile, and sonicate for 10 minutes. Add 10 mL of boiling water, sonicate for 5 minutes, and mix. Add 10 mL of glacial acetic acid, sonicate for 10 minutes, and mix. Add 60 mL of water, mix, and allow to cool to room temperature. Dilute the contents of Flask 2 with water to volume, and add 5.0 mL of the solution from Flask 2 to Flask 1. Dilute the contents of Flask 1 with water to volume, and mix. If necessary, quantitatively dilute with a solution of acetonitrile, glacial acetic acid, and water (10:10:80) to obtain a final concentration of about 0.5 mg per mL. Filter a portion of this solution, discarding the first 3 mL of the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

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 responses of the major peaks. Calculate the quantity, in mg, of triamterene (C12H11N7) in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Triamterene RS in the Standard preparation; V is the sample dilution volume, in mL, considering the 100-mL volume of the solution in Flask 1 and any subsequent dilution factor, if used; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.