Medium: simulated gastric fluid (without enzyme);900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C17H16ClN3Odissolved from UVabsorbances at the wavelength of maximum absorbance at about 294nm of filtered portions of the solution under test,suitably diluted with Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Amoxapine RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C17H16ClN3Ois dissolved in 30minutes.

0.01M Monobasic sodium phosphate— Dissolve 2.76g of monobasic sodium phosphate in 2000mLof water,and mix.

1M Tetramethylammonium chloride— Dissolve 11.3g of tetramethylammonium chloride in 100mLof water,and mix.

Mobile phase— Transfer 40.0mLof 1M Tetramethylammonium chloride,4.0mLof dilute phosphoric acid (1in 5),and 720mLof acetonitrile to a 2000-mLvolumetric flask.Dilute with 0.01M Monobasic sodium phosphateto volume,mix,and filter.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Transfer about 50mg of USP Amoxapine RS,accurately weighed,to a 50-mLvolumetric flask,add 30mLof acetonitrile,and shake by mechanical means to dissolve.Dilute with acetonitrile to volume,and mix.Quantitatively dilute a portion of this solution with Mobile phaseto obtain a solution having a known concentration of about 0.1mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 50mg of amoxapine,to a 50-mLvolumetric flask,add 40mLof Mobile phase,and shake vigorously by mechanical means for 20minutes.Dilute with Mobile phaseto volume,mix,and filter.Pipet 5.0mLof the filtrate into a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor for the analyte peak is not more than 1.8,the column efficiency determined from the analyte peak is not less than 1200theoretical plates,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 areas for the major peaks.Calculate the quantity,in mg,of amoxapine (C17H16ClN3O)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Amoxapine RSin the Standard preparation;and rUand rSare the amoxapine peak areas obtained from the Assay preparationand the Standard preparation,respectively.