Identification—
Transfer a quantity of Topical Solution,equivalent to about 0.5mg of fluocinolone acetonide,to a separator,add 5mLof water,and extract with 10mLof chloroform.Withdraw the chloroform layer into a second separator,wash with 10mLof water,and dry about 2mLof the chloroform extract over about 200mg of anhydrous sodium sulfate:the dried extract responds to the
Thin-Layer Chromatographic Identification Test á201ñ,50µLof the dried chloroform extract and 50µLof the Standard solution being applied,and a mixture of chloroform and diethylamine (2:1)being used for development.
Assay—
Internal standard solution—
Dissolve norethindrone in acetonitrile to obtain a solution containing about 200µg per mL.
Standard preparation—
Dissolve an accurately weighed quantity of
USP Fluocinolone Acetonide RSin acetonitrile to obtain a solution having a known concentration of about 200µg per mL.Transfer 5.0mLof this solution,4.0mLof
Internal standard solution,10mLof propylene glycol,and about 25mLof acetonitrile to a 50-mLvolumetric flask.Mix,cool to room temperature,dilute with acetonitrile to volume,and mix.The final concentration of
USP Fluocinolone Acetonide RSis 20µg per mL.
Mobile solvent—
Prepare a mixture of water and acetonitrile (3:2).Adjust the ratio as necessary to obtain suitable chromatographic performance.
Assay preparation—
Transfer an accurately measured volume of Topical Solution,equivalent to about 0.5mg of fluocinolone acetonide,to a 25-mLvolumetric flask.Add 2.0mLof Internal standard solutionand 10mLof acetonitrile.Mix,cool to room temperature,dilute with acetonitrile to volume,and mix.
Apparatus—
Use a suitable high-pressure liquid chromatograph (see
Chromatography á621ñ)of the general type equipped with a detector for monitoring UVabsorbance at about 254nm,and capable of providing a flow rate of about 2mLper minute for the
Mobile solvent.Use a column containing packing L1so as to provide a resolution factor,
R,of at least 2.0between peaks for norethindrone and fluocinolone acetonide.
Procedure—
Chromatograph equal volumes of the
Assay preparationand the
Standard preparation,adjusting the system as necessary to obtain peaks of between about 50%and 90%full-scale.Calculate the quantity,in mg,of C
24H
30F
2O
6in each mLof the Topical Solution taken by the formula:
0.025(C/V)(RU/RS),
in which
Cis the concentration,in µg per mL,of
USP Fluocinolone Acetonide RSin the
Standard preparation;Vis the volume,in mL,of Solution taken;and
RUand
RSare the ratios of the areas of the fluocinolone acetonide peak to the internal standard peak obtained from the
Assay preparationand the
Standard preparation,respectively.