Identification—
Transfer a quantity of Topical Solution,equivalent to about 1.5mg of clobetasol propionate,to a 50-mLseparator,add 5mLof water,and extract with 5mLof chloroform.Collect the lower layer through a cotton wool plug and evaporate with the aid of a stream of nitrogen to dryness.Dissolve the residue in about 2mLof chloroform to obtain the test solution.Prepare a Standard solution of
USP Clobetasol Propionate RShaving the same concentration as the test solution.The test solution so obtained responds to the
Thin-Layer Chromatographic Identification Test á201ñ,a mixture of chloroform,acetone,and alcohol (100:10:5)being used as the developing solvent.
Microbial limits á61ñ—
It meets the requirements of the tests for absence of
Staphylococcus aureus,
Pseudomonas aeruginosa,
Escherichia coli,and
Salmonellaspecies,and the total aerobic microbial count does not exceed 100cfu per g.
Assay—
[NOTE—Where peak responses are indicated,use peak areas.
]
Mobile phase,Internal standard solution,Standard preparation,System suitability solution,and Chromatographic system—
Proceed as directed in the
Assayunder
Clobetasol Propionate.
Assay preparation—
Transfer an accurately weighed portion of Topical Solution,equivalent to about 1.0mg of clobetasol propionate,to a 25-mLvolumetric flask.Add 10.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix.
Procedure—
Separately inject equal volumes (about 10µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 1.0for clobetasol propionate and 1.6for beclomethasone dipropionate.Calculate the quantity,in mg,of C
25H
32ClFO
5in the portion of Topical Solution taken by the formula:
25C(RU/RS),
in which
Cis the concentration,in mg per mL,of
USP Clobetasol Propionate RSin the
Standard preparation,and
RUand
RSare the ratios of the clobetasol propionate peak to the internal standard peak obtained from the
Assay preparationand the
Standard preparation,respectively.