Identification—
A:
The UVabsorption spectrum of the solution from the Capsule contents obtained in the Assayexhibits maximum absorption at the same wavelength as that of the Standard solution,and the two spectra are similar between 260nm and 350nm.
B:
Shake a portion of the contents of Capsules,equivalent to about 500mg of flucytosine,with 10mLof water.Filter,and to 2mLof the filtrate add 1mLof sodium pentacyanoaminoferrate reagent [prepared by dissolving 100mg of sodium (tri)pentacyanoaminoferrate in 20mLof sodium carbonate solution (1in 100)]and 1mLof 3percent hydrogen peroxide:on standing,a darker green is produced than that produced by a blank.
Dissolution á711ñ—
Medium:
water;900mL.
Apparatus 2:
75rpm.
Time:
60minutes.
Procedure—
Determine the amount of C
4H
4FN
3Odissolved by employing UVabsorption at the wavelength of maximum absorbance at about 276nm on filtered portions of the solution under test,suitably diluted with
Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of
USP Flucytosine RSin the same
Medium.
Tolerances—
Not less than 80%(Q)of the labeled amount of C4H4FN3Ois dissolved in 60minutes.
Assay—
Weigh the contents of not fewer than 20Capsules,and determine the average weight per Capsule.Mix the combined contents,and transfer an accurately weighed portion of the powder,equivalent to about 250mg of flucytosine,to a 250-mLvolumetric flask.Add about 50mLof 0.1Nhydrochloric acid,shake by mechanical means for 30minutes,then add 0.1Nhydrochloric acid to volume,mix,and filter,discarding the first 20mLof the filtrate.Dilute 10mLof the clear filtrate with 0.1Nhydrochloric acid to 250mL.Dilute 10.0mLof this solution with 0.1Nhydrochloric acid to 50mL.Dissolve an accurately weighed quantity of
USP Flucytosine RSin 0.1Nhydrochloric acid,and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 8µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 285nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of flucytosine (C
4H
4FN
3O)in the portion of Capsule contents taken by the formula:
31.25C(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Flucytosine RSin the Standard solution;and
AUand
ASare the absorbances of the solution from the Capsule contents and the Standard solution,respectively.