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.

Phosphate buffer— Transfer about 2.68grams of dibasic sodium phosphate,heptahydrate to a 1-Lvolumetric flask,add 950mLof water,and adjust to a pHof 3.0with phosphoric acid,dilute to volume,and mix.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and Phosphate buffer(7:3).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Prochlorperazine Maleate RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of prochlorperazine of about 0.1mg per mL.

Assay preparation— Transfer an accurately measured portion of Injection,equivalent to about 10mg of prochlorperazine,to a 100-mLvolumetric flask,dissolve in Mobile phase,and dilute with Mobile phaseto volume.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.The column temperature is maintained at 40.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 3000theoretical plates,the tailing factor is not more than 2.5,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of prochlorperazine (C20H24ClN3S)in the portion of Injection taken by the formula: in which 373.94and 606.09are the molecular weights of prochlorperazine and prochlorperazine maleate,respectively,Cis the concentration,in mg per mL,of USP Prochlorperazine Maleate RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.