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

Apparatus 1: 100 rpm.

Time: 60 minutes.

Mobile phase— Prepare a pH 4.0 degassed and filtered mixture of methanol and 0.05 M monobasic potassium phosphate buffer (60:40). Add 1 N sodium hydroxide or phosphoric acid, if necessary, to adjust the mixture to a pH of 4.0. Make adjustments if necessary (see System Suitability under Chromatography 621).

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed under Procedure: the relative standard deviation for replicate injections is not more than 3.0%, and the tailing factor is not more than 2.0.

Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and filtered portions of the solution under test into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity of C21H23ClFNO2 dissolved in comparison with a Standard solution having a known concentration of USP Haloperidol RS in the same medium and similarly chromatographed.

Tolerances— Not less than 80% (Q) of the labeled amount of C21H23ClFNO2 is dissolved in 60 minutes.

Procedure for content uniformity— Transfer 1 finely powdered Tablet to a suitable volumetric flask, and prepare a solution containing about 20 µg per mL by adding warm methanol, shaking for 15 minutes, diluting with methanol to volume, and filtering, discarding the first 20 mL of the filtrate. Concomitantly determine the absorbances of this solution and of a solution of USP Haloperidol RS in the same medium, having a known concentration of about 20 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 245 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C21H23ClFNO2 in the Tablet by the formula: in which T is the labeled quantity, in mg, of haloperidol in the Tablet; D is the concentration, in µg per mL, of the solution from the Tablet, based upon the labeled quantity per Tablet and the extent of dilution; C is the concentration, in µg per mL, of USP Haloperidol RS in the Standard solution; and AU and AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.

Mobile phase— Prepare a pH 4.0 degassed and filtered mixture of methanol and 0.05 M monobasic potassium phosphate buffer (60:40). Add 1 N sodium hydroxide or phosphoric acid, if necessary, to adjust the mixture to a pH of 4.0. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Haloperidol RS in Mobile phase and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.1 mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 10 mg of haloperidol, to a 100-mL volumetric flask, add 60 mL of Mobile phase, sonicate for 10 minutes, and shake by mechanical means for about 1 hour. Dilute with Mobile phase to volume, mix, and filter, discarding the first 20 mL of the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed under Procedure: the tailing factor 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 15 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 C21H23ClFNO2 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Haloperidol RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.