Dichlorphenamide Tablets
»Dichlorphenamide Tablets contain not less than 92.0percent and not more than 108.0percent of the labeled amount of C6H6Cl2N2O4S2.
Packaging and storage—
Preserve in well-closed containers.
Identification—
A:
The polarogram of the solution employed for measurement in the Assayexhibits a half-wave potential (E½)within 1%of that of USP Dichlorphenamide RS,similarly measured (E½is about -1.42volts against a saturated calomel electrode).
B:
Fuse a quantity of powdered Tablets,equivalent to 200mg of dichlorphenamide,with 1pellet of sodium hydroxide:the ammonia fumes produced cause moistened red litmus paper to turn blue.The fusion mixture responds to the tests for Sulfite á191ñ.
Dissolution á711ñ—
Medium:
0.1MpH8.0phosphate buffer (see Buffer Solutionsin the section Reagents,Indicators,and Solutions);900mL.
Apparatus 2:
75rpm.
Time:
60minutes.
Procedure—
Determine the amount of C6H6Cl2N2O4S2dissolved from UVabsorbances at the wavelength of maximum absorbance at about 285nm of filtered portions of the solution under test,suitably diluted with Dissolution Mediumin comparison with a Standard solution having a known concentration of USP Dichlorphenamide RSin the same Medium.
Tolerances—
Not less than 80%(Q)of the labeled amount of C6H6Cl2N2O4S2is dissolved in 60minutes.
Uniformity of dosage units á905ñ:
meet the requirements.
Assay—
Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 50mg of dichlorphenamide,to a 50-mLvolumetric flask.Add about 40mLof dimethylformamide,shake for 5minutes to dissolve the dichlorphenamide,and add dimethylformamide to volume.Pipet 10mLof this suspension into a 100-mLvolumetric flask,add 25.0mLof 0.1Ntetramethylammonium bromide,and dilute with water to volume.Transfer a portion of this solution to a polarographic cell that is immersed in a water bath regulated at 24.5
to 25.5.Deaerate by bubbling purified nitrogen through the solution for 5minutes.Insert the dropping mercury electrode of a suitable polarograph,and record the polarogram from -0.80volt to -1.80volts,using a saturated calomel electrode as the reference electrode,and a galvanometer having a sensitivity of about 5microamperes full scale.Determine the height of the diffusion current at -1.65volts.Calculate the quantity,in mg,of C6H6Cl2N2O4S2in the portion of Tablets taken by the formula:
to 25.5.Deaerate by bubbling purified nitrogen through the solution for 5minutes.Insert the dropping mercury electrode of a suitable polarograph,and record the polarogram from -0.80volt to -1.80volts,using a saturated calomel electrode as the reference electrode,and a galvanometer having a sensitivity of about 5microamperes full scale.Determine the height of the diffusion current at -1.65volts.Calculate the quantity,in mg,of C6H6Cl2N2O4S2in the portion of Tablets taken by the formula:
500C[(id)U/(id)S],
in which (id)Uis the observed diffusion current of the assay solution and (id)Sis that determined similarly in a solution of USP Dichlorphenamide RSthe concentration of which is Cmg per mL(about 100µg per mL).
Auxiliary Information—
Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 625
Phone Number:1-301-816-8389