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

A: Place a quantity of Suppositories,equivalent to about 5mg of prochlorperazine,in a test tube,add 4mLof dilute hydrochloric acid (1in 2),warm on a steam bath to melt the solid,and swirl to mix:a pink color develops in the aqueous layer.

B: To the solution from Identificationtest Aadd 10mLof bromine TS,and mix:essentially no color change occurs (distinction from chlorpromazine,which immediately produces a green color).

Standard preparation— Transfer about 40mg of USP Prochlorperazine Maleate RS,accurately weighed,to a 250-mLseparator containing 75mLof ether.Add 0.5mLof 6Nammonium hydroxide,and proceed as directed for Assay preparation,beginning with “Extract with four 65-mLportions of dilute hydrochloric acid (1in 100).”

Assay preparation— Weigh,mash,and then mix not less than 15Suppositories.Transfer an accurately weighed quantity of the mass,equivalent to about 25mg of prochlorperazine,to a 100-mLbeaker.Dissolve in 50mLof ether,and transfer to a 250-mLseparator with the aid of three 25-mLportions of ether.Extract with four 65-mLportions of dilute hydrochloric acid (1in 100),collecting the aqueous extracts in a 500-mLvolumetric flask.Aerate the combined extracts for 15to 20minutes to remove dissolved ether.Add dilute hydrochloric acid (1in 100)to volume,and mix.Filter a portion of the solution through filter paper,discarding the first 25mLof the filtrate.To 25.0mLof the subsequent filtrate add dilute hydrochloric acid (1in 100)to make 200.0mL,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at 254nm and at 278nm,with a suitable spectrophotometer,using dilute hydrochloric acid (1in 100)as the blank.Calculate the quantity,in mg,of C20H24ClN3Sin the portion of Suppositories taken by the formula: in which 0.617is the ratio of the molecular weight of prochlorperazine to that of prochlorperazine maleate,Wis the weight,in mg,of USP Prochlorperazine Maleate RSin the Standard preparation,and the parenthetic expressions are the differences in the absorbances of the two solutions at the wavelengths indicated by the subscripts,for the Assay preparation(U)and the Standard preparation(S),respectively.