5-Fluorocytosine (5-FC) CAS 2022-85-7 Purity ≥99.5% (HPLC) Capecitabine Emtricitabine Intermediate Factory

5-Fluorocytosine (5-FC) CAS: 2022-85-7 Analysis Method
Appearance-White or Almost White Crystalline Powder
Loss on Drying-Dry it at 105 for 4 hours: it loses not more than 1.50% of its weight.
Residue on Ignition-not more than 0.1%.
Heavy Metals-not more than 0.002%.
Fluoride-Mix 70 mL of freshly prepared saturated potassium chloride solution with 30 mL of isopropyl alcohol, fill the electrode with the clear supernatant, and allow the electrode to remain in the mixture for not less than 2 hours prior to use, or preferably overnight.
When taking the measurements, transfer the solution to a 150-mL beaker, 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 1 to 2 minutes). 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 100 mL, 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 100 mL. Calculate the percentage of fluoride in the portion of Flucytosine taken by the formula:
C / 10
in which C is the fluoride concentration, in mg per 100 mL, from the standard curve: not more than 0.05% of fluoride is found.
Fluorouracil-Dissolve 250 mg in 10 mL of a mixture of glacial acetic acid and water (4:1). Apply 20 µL of this solution to a thin-layer chromatographic plate coated with a 0.5-mm layer of chromatographic silica gel mixture. To the same plate apply 20 µL, in 10-µL increments, of a 0.025 mg per mL solution of USP Fluorouracil RS in 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 14 cm 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 UV radiation: any spot from the solution under test is not greater in size and intensity than the spot at the respective RF produced by the Standard solution, corresponding to not more than 0.1% of fluorouracil.
Assay-Place about 400 mg of Flucytosine, accurately weighed, in a 250-mL beaker, add 150 mL of a mixture of 2 volumes of glacial acetic acid and 1 volume of acetic anhydride, and dissolve, warming gently if necessary. Titrate potentiometrically with 0.1 N perchloric acid VS, using a calomel-glass electrode system. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 12.91 mg of C4H4FN3O. Flucytosine contains not less than 98.5 percent and not more than 101.0 percent of C4H4FN3O, calculated on the dried basis.