Standard preparation
Dissolve about 25 mg of
USP Fludrocortisone Acetate RS, accurately weighed, in chloroform to make 250 mL, and mix. Pipet 10 mL of this solution into a 50-mL volumetric flask, add chloroform to volume, and mix.
Procedure
Pipet 10 mL of the
Assay preparation and the
Standard preparation, respectively, into separate 25-mL volumetric flasks, and pipet 10 mL of chloroform into a third flask to provide a blank. Treat each flask as follows. Add 1.0 mL of a solution prepared by dissolving 50 mg of blue tetrazolium in 10 mL of methanol, and mix. Add 1.0 mL of a mixture of 1 volume of
tetramethylammonium hydroxide TS and 4 volumes of methanol, mix, and allow to stand for 10 minutes. Dilute with a 1 in 100 solution of hydrochloric acid in methanol to volume. Concomitantly determine the absorbances of the solutions from the
Assay preparation and the
Standard preparation in 1-cm cells at about 525 nm, with a suitable spectrophotometer, against the reagent blank. Calculate the quantity, in mg, of C
23H
31FO
6 in the portion of Fludrocortisone Acetate taken by the formula:
1.25C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Fludrocortisone Acetate RS in the
Standard preparation; and
AU and
AS are the absorbances of the solutions from the
Assay preparation and the
Standard preparation, respectively.