Flucytosine
;)
Cytosine,5-fluoro-.
5-Fluorocytosine [2022-85-7].
»Flucytosine contains not less than 98.5percent and not more than 101.0percent of C4H4FN3O,calculated on the dried basis.
Packaging and storage—
Preserve in tight,light-resistant containers.
Identification—
Solution:
8µg per mL.
Medium:
dilute hydrochloric acid (1in 100).
Absorptivities at 285nm,calculated on the dried basis,do not differ by more than 2.0%.
B:
The RFvalue of the principal spot in the specimen chromatogram in the test for Fluorouracilcorresponds to that obtained with the solution of USP Flucytosine RS.
Loss on drying á731ñ—
Dry it at 105
for 4hours:it loses not more than 1.5%of its weight.
for 4hours:it loses not more than 1.5%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Heavy metals,Method IIá231ñ:
0.002%.
Fluoride ions—
[NOTE—All glassware and/or plasticware used in this test should be scrupulously clean and even free from trace amounts of fluoride.The use of plasticware to contain the solutions while the potential is measured is recommended.]
Buffer solution—
To 110g of sodium chloride in a 2-liter volumetric flask add 1g of sodium citrate and 700mLof water,and dissolve with shaking.Carefully add 150g of sodium hydroxide,and dissolve with shaking.Cool to room temperature,and while stirring,cautiously add 450mLof glacial acetic acid.Cool to room temperature,add 600mLof isopropyl alcohol,dilute with water to volume,and mix.The pHof this solution is between 5.0and 5.5.
Standard stock solution—
Accurately weigh 2.211g of sodium fluoride,previously dried at 150for 4hours,into a 1-Lvolumetric flask,and dissolve in about 200mLof water.Add 1.0mLof sodium hydroxide solution (1in 250),dilute with water to volume,and mix.Each mLof this solution contains 1mg of fluoride ion.Store the solution in a closed plastic container.
for 4hours,into a 1-Lvolumetric flask,and dissolve in about 200mLof water.Add 1.0mLof sodium hydroxide solution (1in 250),dilute with water to volume,and mix.Each mLof this solution contains 1mg of fluoride ion.Store the solution in a closed plastic container.
Standard preparations—
Dilute a portion of Standard stock solutionquantitatively and stepwise with Buffer solutionto obtain a Standard preparationhaving a fluoride concentration of 1µg per mL.Prepare the final dilution in a 100-mLvolumetric flask.In the same manner,prepare additional Standard preparationshaving fluoride concentrations of 3,5,and 10µg per mL,respectively.
Test preparation—
Place 1g of Flucytosine,accurately weighed,in a 100-mLvolumetric flask,and dissolve in and dilute with Buffer solutionto volume.
Procedure—
Concomitantly measure the potential (see Titrimetry á541ñ),in mV,of the Standard preparationsand the Test preparation,with a suitable pHmeter equipped with a fluoride-specific ion electrode and a glass-sleeved calomel reference electrode that has been modified in the following manner.Mix 70mLof freshly prepared saturated potassium chloride solution with 30mLof isopropyl alcohol,fill the electrode with the clear supernatant,and allow the electrode to remain in the mixture for not less than 2hours prior to use,or preferably overnight.
When taking the measurements,transfer the solution to a 150-mLbeaker,and immerse the electrodes.Insert a polytef-coated stirring bar into the beaker,place the beaker on a magnetic stirrer having an insulated top,and allow to stir until equilibrium is attained (about 1to 2minutes).Rinse and dry the electrodes between measurements,taking care not to scratch the crystal in the specific ion electrode.
Measure the potential of each Standard preparation,and plot the fluoride concentration,in mg per 100mL,versus the potential,in mV,on semilogarithmic paper.Measure the potential of the Test preparation,and determine from the standard curve the fluoride concentration,in mg per 100mL.Calculate the percentage of fluoride in the portion of Flucytosine taken by the formula:
C/10,
in which Cis the fluoride concentration,in mg per 100mL,from the standard curve:not more than 0.05%of fluoride is found.
Fluorouracil—
Dissolve 250mg in 10mLof a mixture of glacial acetic acid and water (8:2).Apply 20µLof this solution to a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.5-mm layer of chromatographic silica gel mixture.To the same plate apply 20µL,in 10-µLincrements,of a 1in 40,000solution of USP Fluorouracil RSin a mixture of glacial acetic acid and water (4:1).Develop the chromatogram in a mixture of chloroform and glacial acetic acid (13:7)until the solvent front has moved not less than 14cm from the origin.Remove the plate from the developing chamber,and allow the solvent to evaporate.Locate the spots on the plate by observing under short-wavelength UVradiation:any spot from the solution under test is not greater in size and intensity than the spot at the respective RFproduced by the Standard solution,corresponding to not more than 0.1%of fluorouracil.
Organic volatile impurities,Method Vá467ñ:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Assay—
Place about 400mg of Flucytosine,accurately weighed,in a 250-mLbeaker,add 150mLof a mixture of 2volumes of glacial acetic acid and 1volume of acetic anhydride,and dissolve,warming gently if necessary.Titrate potentiometrically with 0.1Nperchloric acid VS,using a calomel-glass electrode system.Perform a blank determination,and make any necessary correction.Each mLof 0.1Nperchloric acid is equivalent to 12.91mg of C4H4FN3O.
Auxiliary Information—
Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 829
Pharmacopeial Forum:Volume No.30(5)Page 1621
Phone Number:1-301-816-8394