Identification—
Transfer the contents of 1tube of Ophthalmic Ointment to a 100-mLbeaker,add about 25mLof alcohol,and stir by mechanical means for about 15minutes.Filter,and use the clear solution as the
Test preparation.Prepare Standard solutions in alcohol containing 0.7mg per mLof
USP Prednisolone Acetate RSand 14mg per mLof
USP Sulfacetamide Sodium RS.Apply separately 10µLof the
Test preparationand 10µLof each Standard solution to a suitable thin-layer chromatographic plate (see
Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Position the plate in a chromatographic chamber,and develop the chromatograms in a solvent system consisting of a mixture of chloroform,heptane,alcohol,and water (50:50:50:2)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.Examine the plate under UVlight:the
Test preparationexhibits two spots whose
RFvalues and intensities correspond to the respective spots from the Standard solutions.
Assay for sulfacetamide sodium—
Mobile phase—
Prepare a filtered and degassed mixture of water,methanol,and glacial acetic acid (890:100:10).Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Standard preparation—
Transfer about 50mg of
USP Sulfacetamide Sodium RS,accurately weighed,to a 40-mLcentrifuge tube.Add 10.0mLof dilute methanol (1in 5),insert the stopper in the tube,and mix,using a vortex mixer for about 3minutes to dissolve the standard.Add 7.5mLof heptane,insert the stopper in the tube,and mix,using a vortex mixer for another 3minutes.Centrifuge to effect separation of the phases.Withdraw and discard the upper,heptane layer.Transfer 3.0mLof the bottom layer to a 500-mLvolumetric flask,add dilute methanol (1in 5)to volume,and mix.
Assay preparation—
Transfer an accurately weighed quantity of Ophthalmic Ointment,equivalent to about 100mg of sulfacetamide sodium,to a 40-mLcentrifuge tube.Add 15.0mLof heptane,insert the stopper in the tube,and mix,using a vortex mixer for about 3minutes to dissolve the Ointment.Add 20.0mLof dilute methanol (1in 5),insert the stopper in the tube,and mix,using a vortex mixer for 3minutes.Centrifuge to effect separation of the phases.Withdraw and discard the upper,heptane layer.Transfer 3.0mLof the bottom layer into a 500-mLvolumetric flask,add dilute methanol (1in 5)to volume,and mix.
System suitability preparation—
Dissolve 3mg of sulfanilamide in 100mLof the Standard preparation,and mix.
Chromatographic system
(see
Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the
Standard preparationand the
System suitability preparation,and record the peak responses as directed for
Procedure:the column efficiency determined for the analyte peak is not less than 1500theoretical plates,the resolution,
R,between the sulfacetamide and sulfanilamide peaks is not less than 3,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 90µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C
8H
9N
2NaO
3S·H
2Oin the portion of Ophthalmic Ointment taken by the formula:
3.33(254.24/236.23)C(rU/rS),
in which 254.24and 236.23are the molecular weights of sulfacetamide sodium monohydrate and anhydrous sulfacetamide sodium,respectively,
Cis the concentration,in µg per mL,calculated on the anhydrous basis,of
USP Sulfacetamide Sodium RSin the
Standard preparation,and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.
Assay for prednisolone acetate—
Mobile phase—
Prepare a filtered and degassed mixture of water and acetonitrile (60:40).Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Internal standard solution—
Transfer about 70mg of norethindrone to a 100-mLvolumetric flask,add dilute methanol (9in 10)to volume,and mix.
Standard preparation—
Transfer about 20mg of
USP Prednisolone Acetate RS,accurately weighed,to a 25-mLvolumetric flask,add dilute methanol (9in 10)to volume,and mix.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,add 5.0mLof
Internal standard solution,add dilute methanol (9in 10)to volume,and mix.
Assay preparation—
Transfer an accurately weighed quantity of Ophthalmic Ointment,equivalent to about 4mg of prednisolone acetate,to a 50-mLcentrifuge tube.Add 10.0mLof heptane,and mix,using a vortex mixer for about 2minutes to dissolve the Ointment.Add 5.0mLof Internal standard solutionand 20.0mLof dilute methanol (9in 10),and mix,using a vortex mixer for 2minutes.Centrifuge to effect separation of the phases.Withdraw and discard the upper,heptane layer.Transfer the lower layer to a 100-mLvolumetric flask.Add dilute methanol (9in 10)to volume,and mix to obtain the Assay preparation.
Chromatographic system
(see
Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the
Standard preparation,and record the peak responses as directed for
Procedure:the column efficiency determined from the analyte peak is not less than 3000,the tailing factor for the analyte peak is not more than 2.5,the resolution,
R,between the analyte and internal standard peaks is not less than 4.5,and the relative standard deviation for replicate injections is not more than 1.5%.
Procedure—
Separately inject equal volumes (about 40µL)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 prednisolone acetate and 1.5for norethindrone.Calculate the quantity,in mg,of C
23H
30O
6in the portion of the Ophthalmic Ointment taken by the formula:
100C(RU/RS),
in which
Cis the concentration,in mg per mL,of
USP Prednisolone Acetate RSin the
Standard preparationtaken;and
RUand
RSare the peak response ratios obtained from the
Assay preparationand the
Standard preparation,respectively.