Ordinary impurities 
466
—
Test solution:
10% water in methanol.
Standard solution:
10% water in methanol.
Eluant:
a mixture of alcohol, water, and ammonium hydroxide (80:16:4).
Visualization:
1.
Assay—
Dissolve about 100 mg of Hydroxychloroquine Sulfate, accurately weighed, in about 5 mL of water, and dilute quantitatively and stepwise with dilute hydrochloric acid (1 in 100) to obtain a solution containing about 10 µg per mL. Similarly prepare a Standard solution of
USP Hydroxychloroquine Sulfate RS. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 343 nm, with a suitable spectrophotometer, using dilute hydrochloric acid (1 in 100) as the blank. Calculate the quantity, in mg, of C
18H
26ClN
3O·H
2SO
4 in the portion of Hydroxychloroquine Sulfate taken by the formula:
10C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Hydroxychloroquine Sulfate RS in the Standard solution; and
AU and
AS are the absorbances of the solution of Hydroxychloroquine Sulfate and the Standard solution, respectively.
;)
for 2 hours: it loses not more than 2.0% of its weight.