Identification—
Solution:
10 µg per mL.
Medium:
dilute hydrochloric acid (1 in 1000).
Ratio:
A 343/A329, between 1.00 and 1.15.
Assay—
Dissolve about 100 mg of Chloroquine Phosphate, accurately weighed, in about 5 mL of water, and dilute quantitatively and stepwise with dilute hydrochloric acid (1 in 1000) to obtain a solution containing about 10 µg per mL. Similarly prepare a Standard solution of
USP Chloroquine Phosphate 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 1000) as the blank. Calculate the quantity, in mg, of C
18H
26ClN
3·2H
3PO
4 in the portion of Chloroquine Phosphate taken by the formula:
10C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Chloroquine Phosphate RS in the Standard solution; and
AU and
AS are the absorbances of the solution of Chloroquine Phosphate and the Standard solution, respectively.
181
, chloroform being substituted for carbon disulfide in the test.
for 16 hours: it loses not more than 2.0% of its weight.