A: Infrared Absorption á197Kñ.

B: The relative retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Buffer solution— Transfer 1.36g of monobasic potassium phosphate to a 1000-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.Adjust the solution with 10%sodium hydroxide (w/v)to a pHof 7.5,and filter.

Mobile phase— Prepare a filtered and degassed mixture of Buffer solutionand acetonitrile (60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a stock solution of propylparaben in methanol having a concentration of 2.5mg per mL.Dilute 25.0mLof the stock solution quantitatively with water to 500.0mL,and mix.

Standard stock solution— Transfer about 50mg of USP Buspirone Hydrochloride RS,accurately weighed,to a 100-mLvolumetric flask,dissolve in 25mLof 1Nhydrochloric acid,dilute with water to volume,and mix.

Standard preparation— Transfer 10.0mLof the Standard stock solutionto a 50-mLvolumetric flask,add 10.0mLof Internal standard solution,dilute with water to volume,and mix.

Assay preparation— Transfer about 50mg of Buspirone Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,add 25mLof 1Nhydrochloric acid,dilute with water to volume,and mix.Transfer 10.0mLof this solution to a 50-mLvolumetric flask,add 10.0mLof the Internal standard solution,dilute with water to volume,and mix.

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 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between buspirone hydrochloride and the internal standard is not less than 4;and the relative standard deviation determined from the buspirone peak response for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times of propylparaben and buspirone hydrochloride are about 0.55and 1.0,respectively.Calculate the quantity,in mg,of C21H31N5O2·HCl in the portion of Buspirone Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Buspirone Hydrochloride RSin the Standard preparation;and RUand RSare the peak response ratios of buspirone hydrochloride to propylparaben obtained from the Assay preparationand the Standard preparation,respectively.