A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Solution: 10 µg per mL.

Medium: methanol.

C: Prepare a solution in methanol containing 500 µg per mL. Apply 100 µL of this solution and 100 µL of a methanol solution of USP Fluorometholone RS containing 500 µg per mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 250-µm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of methylene chloride and acetone (4:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Locate the spots on the plate by examination under short-wavelength UV light: the RF value of the principal spot obtained from the specimen solution corresponds to that obtained from the Standard solution.

Test solution: 10 mg per mL, in pyridine.

(Official January 1, 2007)

Mobile phase— Prepare a suitable filtered solution of methanol and water (60:40) such that the retention time of fluorometholone is about 3 minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Fluorometholone RS in Mobile phase to obtain a solution having a known concentration of about 100 µg per mL.

Assay preparation— Transfer about 20 mg of Fluorometholone, accurately weighed, to a 200-mL volumetric flask, add Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—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 2 mL per minute. Chromatograph six replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, using a suitable microsyringe or sampling valve, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C22H29FO4 in the portion of Fluorometholone taken by the formula: in which C is the concentration, in µg per mL, of USP Fluorometholone RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.