Chromatographic purity
Prepare the test solution by dissolving 50mg of Halcinonide in 5.0mLof a mixture of chloroform and methanol (1:1).Divide the area of a suitable thin-layer chromatographic plate (see
Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture,into three equal sections,the first two sections to be used for the test solution and the third section for the blank.Apply 100µLof the test solution to appropriate sections of the plate,drying each solution as it is applied with a current of warm air.Using a continuous elution chromatographic chamber,develop the chromatogram in a solvent system consisting of a mixture of chloroform and ethyl acetate (5:1)for about 2hours.Remove the plate from the developing chamber,dry in an oven at 90

for 15minutes,and locate the bands by viewing under short-wavelength UVlight.Mark the principal band and any secondary bands.Quantitatively remove the silica gel containing these bands,including a corresponding blank segment,and transfer to separate glass-stoppered,50-mLcentrifuge tubes,combining the impurities if more than one impurity is present.Add 30.0mLof dehydrated alcohol to the tubes containing the principal band and the corresponding blank,and add 10.0mLof dehydrated alcohol to the tubes containing the combined impurities and the corresponding blank.Insert stoppers in the tubes,and shake gently on a reciprocating shaker for about 60minutes.Centrifuge,dilute the principal band eluate and its corresponding blank eluate with an equal volume of dehydrated alcohol,and mix.Determine the absorbances of the clear supernatant eluates in 1-cm cells at the wavelength of maximum absorbance at about 239nm,with a suitable spectrophotometer,using dehydrated alcohol as the blank.Calculate the percentage of chromatographic impurities by the formula:
100Ai/(Ai+6Au),
in which
Aiis the absorbance of the combined impurity bands eluate,corrected for the corresponding blank,and
Auis the absorbance of the principal band eluate,corrected for the corresponding blank.Not more than 3.0%is found.
Assay
Standard preparation
Dissolve an accurately weighed quantity of
USP Halcinonide RSin methanol,and dilute quantitatively and stepwise with methanol to obtain a solution having a known concentration of about 15µg per mL.
Assay preparation
Weigh accurately about 30mg of Halcinonide,transfer to a 100-mLvolumetric flask,dissolve in methanol,dilute with methanol to volume,and mix.Transfer 5.0mLof this solution to a second 100-mLvolumetric flask,dilute with methanol to volume,and mix.
Procedure
Concomitantly determine the absorbances of the
Assay preparationand the
Standard preparationin 1-cm cells at the wavelength of maximum absorbance at about 239nm,with a suitable spectrophotometer,using methanol as the blank.Calculate the quantity,in mg,of C
24H
32ClFO
5in the portion of Halcinonide taken by the formula:
2C(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Halcinonide RSin the
Standard preparation,and
AUand
ASare the absorbances of the
Assay preparationand the
Standard preparation,respectively.