Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 1: 100 rpm.

Time: 30 minutes.

Standard solution— Transfer about 44 mg, accurately weighed, of USP Ofloxacin RS to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix well. Transfer 2.0 mL of this solution into a 100-mL volumetric flask, dilute with Medium to volume, and mix well. The final concentration is about 8.8 µg per mL.

Test solution— Pass a portion of the solution under test through a suitable 0.45-µm filter. Dilute a portion of the filtrate with Medium in such a way as to obtain a final theoretical concentration of about 8.8 µg per mL, considering complete dissolution of the label claim.

Procedure— Determine the amount of C18H20FN3O4 dissolved by employing UV absorption at the wavelength at about 294 nm on the Test solution in comparison with the Standard solution, using a 1-cm cell and Medium as the blank. Calculate the amount, in percentage, of C18H20FN3O4 dissolved by the formula: in which AU and AS are the absorbances obtained from the Test solution and the Standard solution, respectively; CS is the concentration, in mg per mL, of ofloxacin in the Standard solution; DU is the dilution factor of the Test solution; 900 is the volume, in mL, of Medium; 100 is the conversion factor to percentage; and LC is the Tablet label claim, in mg.

Tolerances— Not less than 80% (Q) of the labeled amount of C18H20FN3O4 is dissolved in 30 minutes.

Phosphate buffer— Dissolve 2.72 g of monobasic potassium phosphate in 1000 mL of water. Adjust with diluted phosphoric acid to a pH of 3.3 ± 0.1.

Solution A— Prepare a filtered and degassed mixture of Phosphate buffer and acetonitrile (88:12).

Solution B— Prepare a filtered and degassed mixture of acetonitrile and Phosphate buffer (60:40).

Mobile phase— Use variable mixtures of Solution A and Solution B, as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Dissolve an accurately weighed quantity of USP Ofloxacin RS in methanol, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 4 µg per mL.

Test solution— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of ofloxacin, to a 100-mL volumetric flask, add 70 mL of methanol, and sonicate for about 20 minutes. Dilute with methanol to volume, and mix. Pass a portion of this solution through a filter having a 0.45-µm or finer porosity, discarding the first 5 mL. Use the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 294-nm detector and a 4.6-mm × 10-cm column that contains packing L1. The flow rate is about 1.0 mL per minute. The chromatograph is programmed as follows. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 5.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of each impurity in the portion of Tablets taken by the formula: in which F is the relative response factor for each impurity; rU is the peak response of the impurity obtained from the Test solution; rS is the peak response of ofloxacin obtained from the Standard solution; CS is the concentration, in mg per mL, of USP Ofloxacin RS in the Standard solution; and CU is the concentration, in mg per mL, of ofloxacin in the Test solution, based on the label claim. The impurity limits meet the requirements specified in Table 1.

Buffer solution— Dissolve 2.72 g of monobasic potassium phosphate in 1000 mL of water, and adjust with diluted phosphoric acid to a pH of 3.3 ± 0.1.

Mobile phase— Prepare a filtered and degassed mixture of Buffer solution and acetonitrile (88:12). Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent 1— Prepare a mixture of methanol and glacial acetic acid (75:25).

Diluent 2— Prepare a mixture of water and acetonitrile (90:10).

Standard preparation— Dissolve an accurately weighed quantity of USP Ofloxacin RS in Diluent 1 to obtain a solution having a known concentration of about 1 mg per mL, and dilute quantitatively, and stepwise if necessary, with Diluent 2 to obtain a solution having a known concentration of about 20 µg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of ofloxacin, to a 100-mL volumetric flask, add 70 mL of Diluent 1, and sonicate for about 20 minutes. Dilute with Diluent 1 to volume, and mix. Pass a portion of this solution through a filter having a 0.45-µm or finer porosity, and collect the filtrate. Dilute 2.0 mL of the filtrate with Diluent 2 to 100 mL, and mix well.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 294-nm detector and a 4.6-mm × 10-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 for 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 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 ofloxacin (C18H20FN3O4) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Ofloxacin RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.