A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

C: Prepare a solution of Paramethasone Acetate in a mixture of chloroform and methanol (1:1) containing 2 mg per mL. Apply 10 µL each of this solution and a chloroform-methanol (1:1) solution of USP Paramethasone Acetate RS containing 2 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm 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, nitromethane, and glacial acetic acid (60:40:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, and allow to dry in air for 15 minutes. Return the plate to the developing chamber, and develop again, in the same solvent system, 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 test solution corresponds to that obtained from the Standard solution.

Test solution: 10 mg per mL, in chloroform.

Form A			Form B
d	I/I1		d	I/I1
12.09	10		11.62	20
8.42	20		7.80	8
7.78	10		7.13	10
6.41	100		6.50	60
5.65	100		5.98	100
5.50	10		5.63	70
5.18	2		5.30	100
4.59	30		4.85	60
4.41	20		4.65	60
4.24	40		4.43	8
3.93	20		4.30	2
3.64	30b		3.93	60
3.48	15		3.72	6
3.27	20		3.58	4
3.12	30		3.45	4
3.03	8		3.26	10
2.90	2		3.09	10
2.82	8		2.96	10
2.70	10		2.88	10
2.61	8		2.81	6b
2.51	10		2.66	8b
2.35	2		2.55	6
2.29	8		2.48	6b
2.24	6		2.38	10
2.11	4		2.30	6
2.08	2		2.26	8
2.04	4		2.19	6
2.00	4		2.11	10
1.95	1		2.04	8
1.92	4		1.99	10
1.87	2
1.84	2
1.82	1

(Official January 1, 2007)

Standard preparation— Prepare as directed under Single-Steroid Assay 511, using USP Paramethasone Acetate RS to prepare a solution containing approximately 10 mg per mL.

Assay preparation— Weigh accurately about 50 mg of Paramethasone Acetate, previously dried, dissolve it in a sufficient quantity of a mixture of equal volumes of alcohol and chloroform to make 5.0 mL, and mix.

Procedure— Proceed as directed for Procedure under Single-steroid Assay 511, applying 10 µL each of the Assay preparation and the Standard preparation to the chromatographic plate, and using a solvent system consisting of methylene chloride, nitromethane, and glacial acetic acid (60:40:1), through the fourth sentence of the second paragraph under Procedure. Then centrifuge the tubes for 5 minutes, and determine the absorbances of the supernatants in 1-cm cells at the wavelength of maximum absorbance at about 242 nm, against the blank. Calculate the quantity, in mg, of C24H31FO6 in the portion of Paramethasone Acetate taken by the formula: in which C is the concentration, in mg per mL, of USP Paramethasone Acetate RS in the Standard preparation, and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.