A: Infrared Absorption 197K—Obtain the test specimen as follows. Dissolve about 20 mg of it in 20 mL of methanol, with the aid of gentle heat, and evaporate to dryness. Dry the residue in vacuum at 130 for 3 hours. Proceed as directed with the residue so obtained and a similar preparation of USP Prazosin Hydrochloride RS.

B: Ultraviolet Absorption 197U—

C: Prepare a test solution of it in a mixture of chloroform, methanol, and diethylamine (10:10:1) containing 5 mg per mL, and proceed as directed under Thin-layer Chromatographic Identification Test 201, using a solvent system consisting of a mixture of ethyl acetate and diethylamine (19:1).

D: It responds to the tests for Chloride 191.

Standard preparation— Dissolve 100 mg of iron wire, accurately weighed, in 10 mL of hydrochloric acid, with boiling. Cool, transfer to a 1000-mL volumetric flask, dilute with water to volume, and mix. Dilute quantitatively and stepwise with 0.2 N nitric acid to obtain a solution containing 4.0 µg of iron per mL.

Test preparation— Dissolve the residue obtained in the test for Residue on ignition in 20 mL of 2 N nitric acid. Slowly evaporate this solution to approximately 5 mL, transfer to a 25-mL volumetric flask, using 0.2 N nitric acid as a wash solvent, dilute with 0.2 N nitric acid to volume, and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparation and the Test preparation at the wavelength of maximum absorbance at about 248 nm, with a suitable atomic absorption spectrophotometer (see Apparatus under Spectrophotometry and Light-scattering 851) equipped with an iron hollow-cathode lamp and an air–acetylene flame, using water as the blank: the absorbance of the Test preparation is not more than that of the Standard preparation (0.010%).

Standard preparation— Dissolve 100 mg of nickel, accurately weighed, in 10 mL of nitric acid with the aid of boiling. Cool, transfer to a 1000-mL volumetric flask, dilute with water to volume, and mix. Dilute quantitatively and stepwise with 0.2 N nitric acid to obtain a solution containing 4.0 µg of nickel per mL.

Test preparation— Use the Test preparation prepared as directed in the test for Iron.

Procedure— Concomitantly determine the absorbances of the Standard preparation and the Test preparation at the wavelength of maximum absorbance at about 232 nm, with a suitable atomic absorption spectrophotometer (see Apparatus under Spectrophotometry and Light-scattering 851) equipped with a nickel hollow-cathode lamp and an air–acetylene flame, using water as the blank: the absorbance of the Test preparation is not more than that of the Standard preparation (0.010%).

Test solution: a mixture of chloroform, methanol, and diethylamine (10:10:1).

Standard solution: a mixture of chloroform, methanol, and diethylamine (10:10:1).

Eluant: a mixture of ethyl acetate and diethylamine (19:1).

Visualization: 1.

(Official January 1, 2007)

Mobile phase— Mix 700 mL of methanol, 300 mL of water, and 10 mL of glacial acetic acid. Add diethylamine in sufficient quantity (about 0.2 mL) such that the retention time of prazosin hydrochloride is between 6 and 10 minutes. Degas the solution.

Standard preparation— Transfer about 100 mg of USP Prazosin Hydrochloride RS, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix. Dilute this solution quantitatively with a mixture of methanol and water (7:3) to obtain a solution having a known concentration of about 30 µg per mL.

Assay preparation— Transfer about 100 mg of Prazosin Hydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix. Pipet 3 mL of this solution into a 100-mL volumetric flask, dilute with a mixture of methanol and water (7:3) 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 L3. The flow rate is adjusted to obtain a retention time of between 6 and 10 minutes for prazosin hydrochloride. 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— Inject equal volumes (about 5 µL) of the Standard preparation and the Assay preparation into the chromatograph, using a suitable microsyringe or sampling valve, and measure the peak responses at identical retention times. Calculate the quantity, in mg, of C19H21N5O4·HCl in the Prazosin Hydrochloride taken by the formula: in which C is the concentration, in µg per mL, of USP Prazosin Hydrochloride RS, calculated on the anhydrous basis, in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.