Assay—
Transfer about 100 mg of Ethionamide, accurately weighed, to a 250-mL volumetric flask, dissolve in about 100 mL of methanol, dilute with methanol to volume, and mix. Transfer a 5-mL aliquot to a 200-mL volumetric flask, dilute with methanol to volume, and mix (test solution). Dissolve a suitable quantity of
USP Ethionamide RS, accurately weighed, in methanol, and dilute quantitatively and stepwise with methanol to obtain a Standard solution having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 290 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C
8H
10N
2S in the portion of Ethionamide taken by the formula:
10C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Ethionamide RS in the Standard solution, calculated on the anhydrous basis, and
AU and
AS are the absorbances of the test solution and the Standard solution, respectively.
;)
197U
—Test solution versus standard solution, prepared as directed in the Assay.
and 164