A: Infrared Absorption 197M.

B: Ultraviolet Absorption 197U—

C: A solution (1 in 4000) responds to the tests for Chloride 191.

Benzaldehyde solution— Transfer 1.0 mL of benzaldehyde to a 100-mL volumetric flask, dilute with a mixture of methanol and water (9:1) to volume, and mix.

Acetonitrile solution— Transfer 300 mL of water to a 1000-mL volumetric flask, dilute with acetonitrile to volume, and mix.

Phosphate buffer— Dissolve 5.82 g of dibasic sodium phosphate and 3.81 g of monobasic potassium phosphate in 1000 mL of water, and adjust with either 1 N sodium hydroxide or 1 N phosphoric acid to a pH of 7.0 ± 0.1.

Mobile phase— Dissolve 300 mg of edetate disodium in 300 mL of water in a 1000-mL volumetric flask. Dilute with acetonitrile to volume, mix, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Transfer about 65 mg of hydrazine dihydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with water to volume, and mix to obtain a solution having a known concentration of about 0.65 mg per mL. Dilute this solution quantitatively, and stepwise if necessary, with water to obtain a Standard solution having a known concentration of about 0.325 µg of hydrazine dihydrochloride per mL. Transfer 1.0 mL of the Standard solution to a 10-mL reaction vessel. Add 4.0 mL of Benzaldehyde solution, and shake by mechanical means for 20 minutes. Transfer 2.0 mL of this solution to a 5-mL volumetric flask, dilute with Acetonitrile solution to volume, and mix.

Test solution— [NOTE—Condition the extraction column specified in this procedure in the following manner. Wash the column with two 2.0-mL portions of hexanes, and dry with the aid of vacuum for two minutes. Wash the column with two 2.0-mL portions of methanol, two 2.0-mL portions of water, and two 2.0-mL portions of pH 7.0 phosphate buffer. At no time after the hexanes wash should the column be allowed to dry out.] Transfer about 20 mg of Hydralazine Hydrochloride, accurately weighed, to a 10-mL reaction vessel, and dissolve in 1.0 mL of water. Add 4.0 mL of Benzaldehyde solution, and shake by mechanical means for 20 minutes. Pipet 2.0 mL of this solution into a freshly conditioned solid phase extraction column containing benzenesulfonic acid strong cation-exchange packing with a sorbent-mass to column volume ratio of 500 mg per 3 mL, or equivalent, and elute into a 5-mL volumetric flask. Wash the column with two 1.5-mL portions of Acetonitrile solution, collecting the washings with the eluate, dilute with Acetonitrile solution to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 310-nm detector and a 4.0-mm × 25-cm column that contains 10-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative retention times are about 1.0 for hydralazine derivative and 1.5 for hydrazine derivative; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the solution from the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of hydrazine in the portion of Hydralazine Hydrochloride taken by the formula: in which 32.05 and 104.97 are the molecular weights of hydrazine and hydrazine dihydrochloride, respectively; C is the concentration, in µg per mL, of hydrazine dihydrochloride in the Standard solution; W is the weight, in mg, of Hydralazine Hydrochloride taken for the Test solution; and rU and rS are the hydrazine peak responses obtained from the Test solution and from the solution from the Standard solution, respectively: not more than 0.001% of hydrazine is found.

Mobile phase and Resolution solution— Prepare as directed in the Assay.

Test solution— Transfer about 25 mg of Hydralazine Hydrochloride, accurately weighed, to a 50-mL volumetric flask. Add about 30 mL of 0.1 N acetic acid, and sonicate to dissolve. Cool, dilute with 0.1 N acetic acid to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 230-nm detector and a 4.0-mm × 25-cm column that contains 10-µm packing L10. The flow rate is about 1 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.65 for phthalazine and 1.0 for hydralazine hydrochloride; and the resolution, R, between the phthalazine peak and the hydralazine peak is not less than 4.0.

Procedure— Inject about 20 µL of the Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each peak, other than the solvent peak and the hydralazine peak, in the portion of Hydralazine Hydrochloride taken by the same formula: in which ri is the response of each peak; and rt is the sum of the responses of all the peaks, excluding that of the solvent peak: not more than 1.0% total impurities is found.

(Official January 1, 2007)

Mobile phase— Dissolve 1.44 g of sodium dodecyl sulfate and 0.75 g of tetrabutylammonium bromide in 770 mL of water, and add 230 mL of acetonitrile. Adjust with 0.1 N sulfuric acid to a pH of 3.0, mix, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Hydralazine Hydrochloride RS in 0.1 N acetic acid to obtain a solution having a known concentration of about 0.4 mg per mL. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with 0.1 N acetic acid to volume, and mix to obtain a solution having a known concentration of about 40 µg per mL.

Resolution solution— Prepare a solution in 0.1 N acetic acid containing about 0.25 mg of USP Hydralazine Hydrochloride RS and 0.05 mg of phthalazine per mL. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, dilute with 0.1 N acetic acid to volume, and mix to obtain a solution containing about 25 µg of USP Hydralazine Hydrochloride RS and 5 µg of phthalazine per mL.

Assay preparation— Transfer about 100 mg of Hydralazine Hydrochloride, accurately weighed, to a 250-mL volumetric flask. Dissolve in and dilute with 0.1 N acetic acid to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with 0.1 N acetic acid to volume, mix, and filter, discarding the first 10 mL of the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 230-nm detector and a 4.0-mm × 25-cm column that contains 10-µm packing L10. The flow rate is about 1 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.65 for phthalazine and 1.0 for hydralazine hydrochloride; and the resolution, R, between the phthalazine and hydralazine peaks is not less than 4.0. 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— Separately inject equal volumes (about 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C8H8N4·HCl in the portion of Hydralazine Hydrochloride taken by the formula: in which C is the concentration, in µg per mL, of USP Hydralazine Hydrochloride RS in the Standard preparation; and rU and rS are the hydralazine hydrochloride peak responses obtained from the Assay preparation and the Standard preparation, respectively.