A: Infrared Absorption 197K—

Test specimen— Transfer a quantity of finely powdered Tablets, equivalent to about 100 mg of hydralazine hydrochloride, to a glass-stoppered flask. Add 40 mL of 1 N hydrochloric acid, shake by mechanical means for 5 minutes, and filter, discarding the first few mL of the filtrate. Place 20 mL of the filtrate in a separator, wash with 10 mL of methylene chloride, and discard the methylene chloride washing. Mix the aqueous solution in the separator with 2 mL of sodium nitrite solution (14 in 1000), add 10 mL of methylene chloride, shake by mechanical means for 5 minutes, and allow the layers to separate. Pass the methylene chloride layer through a filter of anhydrous sodium sulfate that previously has been washed with methylene chloride, and collect the solution in a 50-mL beaker. Evaporate with the aid of gentle heat and a stream of dry nitrogen to dryness.

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.

Medium: 0.01 N hydrochloric acid; 900 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C8H8N4·HCl dissolved by employing UV absorption at the wavelength of maximum absorbance at about 260 nm on filtered portions of the solution under test, suitably diluted with Dissolution Medium, in comparison with a Standard solution having a known concentration of USP Hydralazine Hydrochloride RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C8H8N4·HCl is dissolved in 45 minutes.

(Official January 1, 2007)

Mobile phase, Standard preparation, Resolution solution, and Chromatographic system— Prepare as directed in the Assay under Hydralazine Hydrochloride.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of hydralazine hydrochloride, to a 250-mL volumetric flask, dissolve in and dilute with 0.1 N acetic acid to volume, and centrifuge. Pipet 10 mL of the clear liquid into a 100-mL volumetric flask, dilute with 0.1 N acetic acid to volume, mix, and filter.

Procedure— Proceed as directed in the Assay under Hydralazine Hydrochloride. Calculate the quantity, in mg, of hydralazine hydrochloride (C8H8N4·HCl) in the portion of Tablets taken by the formula: in which the terms are as defined therein.