A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

C: Prepare a solution of Paramethasone Acetate in a mixture of chloroform and methanol (1:1)containing 2mg per mL.Apply 10µLeach of this solution and a chloroform-methanol (1:1)solution of USP Paramethasone Acetate RScontaining 2mg per mLto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)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 15minutes.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 UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

Test solution: 10mg 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

Standard preparation— Prepare as directed under Single-Steroid Assay á511ñ,using USP Paramethasone Acetate RSto prepare a solution containing approximately 10mg per mL.

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

Procedure— Proceed as directed for Procedureunder Single-steroid Assay á511ñ,applying 10µLeach of the Assay preparationand the Standard preparationto 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 5minutes,and determine the absorbances of the supernatants in 1-cm cells at the wavelength of maximum absorbance at about 242nm,against the blank.Calculate the quantity,in mg,of C24H31FO6in the portion of Paramethasone Acetate taken by the formula: in which Cis the concentration,in mg per mL,of USP Paramethasone Acetate RSin the Standard preparation,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.