Identification
A:
The UVabsorption spectrum of the solution employed for measurement of absorbance in the
Assayexhibits maxima and minima at the same wavelengths as that of a similar solution of
USP Chloroquine Phosphate RS,concomitantly measured.The ratio
A343/
A329is between 1.00and 1.15.
B:
To 20mLof a dilution of Injection with water,containing about 20mg of chloroquine hydrochloride,add 5mLof trinitrophenol TS:a yellow precipitate is formed.Filter,wash the precipitate with water until the last washing is colorless,and dry over silica gel:the precipitate melts between 205

and 210

.[
CautionPicrates may explode.]
C:
It responds to the tests for Chloride á191ñ.
Assay
Transfer an accurately measured volume of Injection,equivalent to about 150mg of chloroquine hydrochloride,to a 1000-mLvolumetric flask,and dilute with water to volume.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,add 10mLof dilute hydrochloric acid (1in 100),and dilute with water to volume.Dissolve an accurately weighed quantity of
USP Chloroquine Phosphate RSin dilute hydrochloric acid (1in 1000),and dilute quantitatively and stepwise with dilute hydrochloric acid (1in 1000)to obtain a Standard solution having a known concentration of about 10µg per mL.Concomitantly determine the absorbances of both solutions at the wavelength of maximum absorbance at about 343nm,with a suitable spectrophotometer,using water as the blank.Calculate the quantity,in mg,of C
18H
26ClN
3·2HCl in the portion of Injection taken by the formula:
15.23C(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Chloroquine Phosphate RSin the Standard solution,and
AUand
ASare the absorbances of the solution from the Injection and the Standard solution,respectively.