A: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation as obtained in the Assay.

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

Mobile phase— Dissolve 2.7 g of sodium acetate in 500 mL of water, add 500 mL of acetonitrile, 2 mL of tetramethylammonium hydroxide solution in methanol (1 in 5), mix, adjust with glacial acetic acid to a pH of 6.5, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

System suitability solution— Transfer about 12.5 mg of benzenesulfonamide to a 25-mL volumetric flask, add 15 mL of methanol, and shake to dissolve. Dilute with 0.01 M phosphoric acid to volume, and mix. Pipet 5 mL of this solution and 5 mL of the stock solution used to prepare the Standard preparation into a 100-mL volumetric flask, dilute with 0.01 M phosphoric acid to volume, and mix.

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

Chromatographic system (see Chromatography 621)—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 1.5 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed under Procedure: the relative retention times are about 0.7 for benzenesulfonamide and 1.0 for 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 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C14H22ClN3O2 in each mL of the Injection taken by the formula: in which 299.80 and 336.26 are the molecular weights of metoclopramide and anhydrous metoclopramide hydrochloride, respectively; C is the concentration, in µg per mL, of USP Metoclopramide Hydrochloride RS, on the anhydrous basis, in the Standard preparation; V is the volume, in mL, of Injection taken; and rU and rS are the peak responses of metoclopramide obtained from the Assay preparation and the Standard preparation, respectively.