Identification
Prepare a test solution by placing a quantity of Cream,equivalent to about 5mg of fluorouracil,in a glass-stoppered conical flask,add 50mLof alcohol,and shake until dissolved.Dissolve 5mg of
USP Fluorouracil RSin 50mLof alcohol to obtain a Standard solution.In 20-µLincrements,apply 100µLeach of the Standard solution and the test solution to a line about 3cm from the bottom edge of a thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture,which previously has been dried and activated at 105

for 5minutes.Develop the chromatogram in a solvent system consisting of a mixture of ethyl acetate,methanol,and ammonium hydroxide (75:25:1),allowing the solvent front to move about 15cm beyond the initial spotting line.Remove the plate,air-dry for 15minutes,and examine under short-wavelength UVlight:the
RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Assay
Mobile phase
,
Standard preparation,and
Chromatographic systemProceed as directed in the
Assayunder
Fluorouracil.
Assay preparation
Transfer an accurately weighed portion of Cream,equivalent to about 10mg of fluorouracil,to a 100-mLvolumetric flask,add 20mLof methanol,and mix on a vortex mixer to dissolve.Dilute with water to volume,and mix.Transfer 1.0mLof this solution to a 10-mLvolumetric flask,dilute with water to volume,mix,and filter.
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.Calculate the quantity,in mg,of fluorouracil (C
4H
3FN
2O
2)in the portion of Cream taken by the formula:
C(rU/rS),
in which
Cis the concentration,in µg per mL,of
USP Fluorouracil RSin the
Standard preparation;and
rUand
rSare the fluorouracil peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.