Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of procarbazine (C12H19N3O) dissolved from UV absorbances at the wavelength of maximum absorbance at about 233 nm of filtered portions of the solution under test, suitably diluted with water, in comparison with a Standard solution having a known concentration of USP Procarbazine Hydrochloride RS in the same medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C12H19N3O is dissolved in 45 minutes.

pH 12 buffer— Dissolve 5.43 mL of phosphoric acid, 4.60 mL of glacial acetic acid, and 4.95 g of boric acid in water to make 2000 mL. To 100 mL of this solution add 100 mL of 0.2 N sodium hydroxide. Prior to use, deaerate this solution by bubbling with scrubbed nitrogen.

Procedure— [note—Use low-actinic glassware throughout this procedure.] Weigh the contents of not less than 20 Capsules, and determine the average weight per capsule. Mix the combined contents to obtain a homogeneous sample. Transfer an accurately weighed portion of this powder, equivalent to about 60 mg of procarbazine hydrochloride, to a 100-mL volumetric flask that previously has been flushed with nitrogen. Dissolve in pH 12 buffer, dilute with pH 12 buffer to volume, and centrifuge a portion of this solution at about 1500 rpm for about 3 minutes. Transfer 10 mL to 15 mL of the solution to a polarographic cell that is regulated at 25 ± 0.1. Deaerate by bubbling scrubbed nitrogen through the solution for 5 minutes. Insert the dropping mercury electrode of a suitable polarograph, which is capable of measuring a current of 10 microamperes, using an average capillary, a mercury column height of 56 cm, and a drop rate of approximately 4 per second. Record the polarogram from 0.75 volt to +0.25 volt, using a saturated calomel electrode as the reference electrode. Determine the height of the current at a point 200 mV anodic of the half-wave potential. Calculate the quantity, in mg, of C12H19N3O in the portion of Capsule contents taken by the formula: in which 0.8585 is the ratio of the molecular weight of procarbazine to that of procarbazine hydrochloride, iU is the observed current of the solution from the Capsule contents and iS is that determined similarly in a solution of USP Procarbazine Hydrochloride RS, the concentration of which is C mg per mL (about 600 µg per mL).