A: It meets the requirements of the Identification test in Gentamicin Injection.

B: The retention time of the prednisolone acetate peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay for prednisolone acetate.

Diluting solvent— Mix 700 mL of methanol and 300 mL of water.

Mobile phase— Prepare a suitable mixture of water and acetonitrile (60:40), and pass through a suitable filter having a porosity of 1 µm or less. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Transfer about 60 mg of USP Prednisolone Acetate RS, accurately weighed, to a 50-mL volumetric flask, dissolve in methanol, dilute with methanol to volume, and mix. Transfer 8.0 mL of this solution to a second 50-mL volumetric flask, dilute with Diluting solvent to volume, and mix. This solution contains about 0.2 mg of USP Prednisolone Acetate RS per mL.

Assay preparation— Transfer an accurately measured volume of well-mixed Ophthalmic Suspension, equivalent to about 10 mg of prednisolone acetate, to a 50-mL volumetric flask, dilute with Diluting solvent to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and measure the peak responses as directed under Procedure: the tailing factor for the analyte peak is not more than 1.25, the column efficiency is not less than 2000 theoretical plates, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 30 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 prednisolone acetate (C23H30O6), in each mL of the Ophthalmic Suspension taken by the formula: in which C is the concentration, in mg per mL, of USP Prednisolone Acetate RS in the Standard preparation; V is the volume, in mL, of Ophthalmic Suspension taken; and rU and rS are the prednisolone acetate peak responses obtained from the Assay preparation and the Standard preparation, respectively.