A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Test solution: 2 mg per mL, in dimethylformamide.

Mobile phase— Prepare a degassed solution containing about 60 volumes of methanol and 40 volumes of water such that the retention times for triamcinolone and hydrocortisone are about 5 and 10 minutes, respectively.

Internal standard solution— Dissolve hydrocortisone in Mobile phase to obtain a solution having a concentration of about 0.3 mg per mL.

Standard preparation— Transfer about 10 mg of USP Triamcinolone RS, accurately weighed, to a 50-mL volumetric flask, dissolve in Internal standard solution, dilute with the same solvent to volume, and mix.

Assay preparation— Using about 10 mg of Triamcinolone, accurately weighed, prepare as directed under Standard preparation.

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 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%, and the resolution factor between triamcinolone and hydrocortisone is not less than 3.0.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph by means of a suitable microsyringe or sampling valve, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C21H27FO6 in the portion of Triamcinolone taken by the formula: in which C is the concentration, in mg per mL, of USP Triamcinolone RS in the Standard preparation, and RU and RS are the peak response ratios of triamcinolone to hydrocortisone obtained from the Assay preparation and the Standard preparation, respectively.