Procedure—
Pipet an aliquot of the filtered test solution, estimated to contain about 278 µg of penicillamine, into a 100-mL volumetric flask. Into a similar flask pipet an equivalent volume of 0.1 N hydrochloric acid to provide a reagent blank, and into a third 100-mL volumetric flask pipet 1 mL of
Standard preparation. Treat each flask as follows. Add by pipet 3 mL of
Sodium nitrite reagent, and mix by swirling occasionally. After 5 minutes, add 10 mL of
Ammonium sulfamate reagent, swirl, and allow to stand for an additional 5 minutes. Add 5 mL of
Sulfanilamide-mercuric chloride reagent, swirl, and immediately add 10 mL of
N-(
1-Naphthyl)
ethylenediamine dihydrochloride reagent. Dilute with water to volume, and mix. Determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 540 nm, with a suitable spectrophotometer, against the reagent blank. Calculate the percentage dissolution of the Capsule taken by the formula:
90(C/WV)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Penicillamine RS in the
Standard preparation; W is the labeled quantity, in mg, of penicillamine in the Capsule;
V is the volume, in mL, of the aliquot of test solution used; and
AU and
AS are the absorbances of the solutions from the test solution and the
Standard preparation, respectively.
711
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for 3 hours: it loses not more than 1.0% of its weight.