Identification
Apply 20µLof a solution prepared as directed for
Assay preparationin the
Assaybut without the addition of the
Internal standard solution,and 20µLof a solution of
USP Triamcinolone Acetonide RSin methanol containing 30µg per mL,to a line parallel to and about 1.5cm from the bottom edge of a thin-layer chromatographic plate (see
Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Proceed as directed in the
Identificationtest under
Triamcinolone Acetonide Cream,beginning with Place the plate in a developing chamber.The specified result is obtained.
Assay
Mobile phase
Prepare a degassed solution of water and acetonitrile (70:30).
Internal standard solution
Dissolve fluoxymesterone in methanol to obtain a solution having a concentration of about 25µg per mL.
Standard preparation
Dissolve an accurately weighed quantity of
USP Triamcinolone Acetonide RSin methanol to obtain a solution having a concentration of about 100µg per mL.Transfer 15.0mLof this solution to a 50-mLvolumetric flask,add 25.0mLof
Internal standard solution,dilute with methanol to volume,and mix.This solution has a known concentration of about 30µg per mL.
Assay preparation
Fit the valve of a previously weighed Triamcinolone Acetonide Aerosol container with a suitable tube assembly so that the contents can be sprayed directly into the bulb portion of a 100-mLvolumetric flask containing 50.0mLof Internal standard solutionand 20mLof methanol.Spray a portion of the contents,equivalent to about 3mg of triamcinolone acetonide,into the flask,determining the exact amount sprayed by difference.Place in a sonic bath for about 5minutes to expel the propellant.Dilute with methanol to volume,and mix.[NOTEThe propellant is extremely flammable.When evaporating,observe proper precautions and work under an explosion-proof hood.]
Procedure
Introduce equal volumes (between 15µLand 25µL)of the
Assay preparationand the
Standard preparationinto a chromatograph (see
Chromatography á621ñ)operated at room temperature and fitted with a 3.9-mm ×30-cm column,packed with packing L1,and equipped with a 254-nm detector.Adjust the operating parameters and the
Mobile phasecomposition such that the separation of triamcinolone acetonide and internal standard is optimized,with a retention time of about 14minutes for triamcinolone acetonide.In a suitable system,the relative standard deviation for five replicate injections of the
Standard preparationis not more than 3.0%.Measure the responses of the internal standard and triamcinolone acetonide peaks at the same retention times obtained from the
Assay preparationand the
Standard preparation.Calculate the quantity,in µg,of C
24H
31FO
6in the portion of Topical Aerosol taken by the formula:
100C(RU/RS),
in which
Cis the concentration,in µg per mL,of
USP Triamcinolone Acetonide RSin the
Standard preparation,and
RUand
RSare the ratios of the peak responses of triamcinolone acetonide to internal standard obtained from the
Assay preparationand the
Standard preparation,respectively.