note—Throughout the following procedures, protect test or assay specimens, the USP Reference Standard, and solutions containing them, by conducting the procedures without delay, under subdued light, or using low-actinic glassware.

for syrup packaged in single-unit containers: meets the requirements.

for syrup packaged in multiple-unit containers: meets the requirements.

Acid-alcohol solution and Palladium chloride solution— Prepare as directed in the Assay under Perphenazine Injection.

Standard preparation— Dissolve an accurately weighed quantity of USP Perphenazine RS in Acid-alcohol solution to obtain a solution having a known concentration of about 160 µg per mL.

Assay preparation— Transfer an accurately measured volume of Syrup, equivalent to about 6 mg of perphenazine, to a 25-mL volumetric flask, dilute with water to volume, and mix. Transfer 10 mL to a 125-mL separator, add 25 mL of water, adjust with ammonium hydroxide to a pH of 10 to 11, and extract with four 20-mL portions of chloroform, filtering the extracts through anhydrous sodium sulfate. Evaporate the combined extracts on a steam bath with the aid of a stream of nitrogen to about 5 mL. Complete the evaporation without application of heat, and dissolve the residue in 15.0 mL of Acid-alcohol solution, filtering if necessary.

Procedure— Mix 10.0 mL each of the Assay preparation and the Standard preparation with 15.0 mL of Palladium chloride solution, filter if necessary, and concomitantly determine the absorbances of these solutions, against a reagent blank, in 1-cm cells at the wavelength of maximum absorbance at about 480 nm, with a suitable spectrophotometer. Calculate the quantity, in mg, of perphenazine (C21H26ClN3OS) in each mL of the Syrup taken by the formula: in which C is the concentration, in µg per mL, of USP Perphenazine RS in the Standard preparation; V is the volume, in mL, of Syrup taken; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.