A: Infrared Absorption 197K—Obtain the test specimen as follows. Steam-distill a volume of Injection, equivalent to about 250 mg of tolazoline hydrochloride, for 5 to 10 minutes, and discard the distillate. Transfer the remaining solution to a separator, add about 2 mL of 1 N sodium hydroxide, and extract with 20 mL of ether. Filter the ether extract through cotton into a beaker, evaporate to dryness, and dry the residue in vacuum over silica gel for 4 hours.

B: It responds to Identification test B under Tolazoline Hydrochloride.

C: To 1 mL of Injection add 1 mL of ammonium reineckate TS: a pink precipitate is formed.

Standard preparation— Transfer about 30 mg of USP Tolazoline Hydrochloride RS, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 150 mg of tolazoline hydrochloride, to a 100-mL volumetric flask, dilute with methanol to volume, and mix. Transfer 20.0 mL of this solution to a second 100-mL volumetric flask, dilute with methanol to volume, and mix.

Procedure— Transfer 3.0 mL each of the Standard preparation, the Assay preparation, and methanol to provide the blank, to separate 25-mL volumetric flasks. To each flask add 1 mL of 0.5 N sodium hydroxide and 1 mL of dilute sodium nitroferricyanide TS (1 in 2), mix, and allow to stand for 10 minutes. Add 3 mL of sodium bicarbonate solution (1 in 12) to each flask, dilute with water to volume, mix, and allow to stand for 10 minutes. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 565 nm, with a suitable spectrophotometer, against the blank. Calculate the quantity, in mg, of C10H12N2·HCl in each mL of the Injection taken by the formula: in which C is the concentration, in µg per mL, of USP Tolazoline 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.