Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of procarbazine (C12H19N3O)dissolved from UVabsorbances at the wavelength of maximum absorbance at about 233nm 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 RSin the same medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C12H19N3Ois dissolved in 45minutes.

pH12buffer— Dissolve 5.43mLof phosphoric acid,4.60mLof glacial acetic acid,and 4.95g of boric acid in water to make 2000mL.To 100mLof this solution add 100mLof 0.2Nsodium 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 20Capsules,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 60mg of procarbazine hydrochloride,to a 100-mLvolumetric flask that previously has been flushed with nitrogen.Dissolve in pH12buffer,dilute with pH12bufferto volume,and centrifuge a portion of this solution at about 1500rpm for about 3minutes.Transfer 10mLto 15mLof the solution to a polarographic cell that is regulated at 25±0.1.Deaerate by bubbling scrubbed nitrogen through the solution for 5minutes.Insert the dropping mercury electrode of a suitable polarograph,which is capable of measuring a current of 10microamperes,using an average capillary,a mercury column height of 56cm,and a drop rate of approximately 4per second.Record the polarogram from -0.75volt to +0.25volt,using a saturated calomel electrode as the reference electrode.Determine the height of the current at a point 200mVanodic of the half-wave potential.Calculate the quantity,in mg,of C12H19N3Oin the portion of Capsule contents taken by the formula: in which 0.8585is the ratio of the molecular weight of procarbazine to that of procarbazine hydrochloride,iUis the observed current of the solution from the Capsule contents and iSis that determined similarly in a solution of USP Procarbazine Hydrochloride RS,the concentration of which is Cmg per mL(about 600µg per mL).