A: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationas obtained in the Assay.

B: Mix a volume of Injection,equivalent to about 50mg of metoclopramide,with 5mLof water and 5mLof a 1in 100solution of p-dimethylaminobenzaldehyde in 1Nhydrochloric acid:a yellow-orange color is produced.

Mobile phase— Dissolve 2.7g of sodium acetate in 500mLof water,add 500mLof acetonitrile,2mLof tetramethylammonium hydroxide solution in methanol (1in 5),mix,adjust with glacial acetic acid to a pHof 6.5,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Metoclopramide Hydrochloride RSin 0.01Mphosphoric acid to obtain a stock solution having a known concentration of about 0.9mg of anhydrous metoclopramide hydrochloride per mL.Dilute quantitatively,and stepwise if necessary,a volume of this stock solution with 0.01Mphosphoric acid to obtain a Standard preparationhaving a known concentration of about 45µg of USP Metoclopramide Hydrochloride RS,on the anhydrous basis,per mL(equivalent to about 40µg of anhydrous metoclopramide per mL).

System suitability solution— Transfer about 12.5mg of benzenesulfonamide to a 25-mLvolumetric flask,add 15mLof methanol,and shake to dissolve.Dilute with 0.01Mphosphoric acid to volume,and mix.Pipet 5mLof this solution and 5mLof the stock solution used to prepare the Standard preparationinto a 100-mLvolumetric flask,dilute with 0.01Mphosphoric acid to volume,and mix.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 40mg of metoclopramide,to a 100-mLvolumetric flask,dilute with 0.01Mphosphoric acid to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with 0.01Mphosphoric acid to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed under Procedure:the relative retention times are about 0.7for benzenesulfonamide and 1.0for metoclopramide,and the resolution,R,between the benzenesulfonamide peak and the metoclopramide peak is not less than 1.5.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the tailing factor for the metoclopramide peak is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)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 C14H22ClN3O2in each mLof the Injection taken by the formula: in which 299.80and 336.26are the molecular weights of metoclopramide and anhydrous metoclopramide hydrochloride,respectively;Cis the concentration,in µg per mL,of USP Metoclopramide Hydrochloride RS,on the anhydrous basis,in the Standard preparation;Vis the volume,in mL,of Injection taken;and rUand rSare the peak responses of metoclopramide obtained from the Assay preparationand the Standard preparation,respectively.