A: Transfer 1 mL of the Injection to a 200-mL volumetric flask, and dilute with water to volume. To 1 mL of this dilution add 2 mL of a solution of 0.02% 8-hydroxyquinoline in 3 N sodium hydroxide, and add 1 mL of 0.1% N-bromosuccinimide solution: an orange color is produced.

B: It meets the requirements of the tests for Chloride 191.

(Official January 1, 2007)

Color reagent— Dissolve 28.0 g of potassium hydroxide and 2.0 g of potassium sodium tartrate in 100 mL of water. Cool, and add, in the order named, 100 mg of 2,4-dichloro-1-naphthol, 180 mL of alcohol, and 20.0 mL of 0.475% sodium hypochlorite solution. Mix by swirling, and allow to stand at room temperature for 1 hour before using. This Color reagent may be stored in a glass-stoppered bottle, in a refrigerator, for 2 months.

Standard preparation— Dissolve an accurately weighed quantity of USP Arginine Hydrochloride RS in water, and dilute quantitatively and stepwise with water to obtain a solution having a known concentration of about 40 µg per mL.

Assay preparation— Pipet into a 100-mL volumetric flask a volume of Injection, equivalent to 200 mg of arginine hydrochloride, add water to volume, and mix. Pipet 5 mL of this solution into a 250-mL volumetric flask, add water to volume, and mix.

Procedure— Transfer 2.0-mL portions of the Assay preparation and the Standard preparation, respectively, to separate flasks, and treat each as follows. Add 2.0 mL of potassium iodide solution (3 in 1000), mix, and allow to stand for 15 minutes. Add 6.0 mL of Color reagent, mix, and allow to stand for 15 minutes. Add 2.0 mL of sodium hypochlorite solution (19 in 10,000), mix, and allow to stand for 15 minutes. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 520 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of C6H14N4O2·HCl in each mL of the Injection taken by the formula: in which C is the concentration, in µg per mL, of USP Arginine Hydrochloride RS in the Standard preparation; V is the volume, in mL, of Injection taken; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.