Identification—
The UV absorption spectrum of the solution of chlorothiazide prepared from Oral Suspension as directed in the
Assay exhibits maxima and minima at the same wavelengths as that of a solution of
USP Chlorothiazide RS, prepared as directed in the
Assay, concomitantly measured.
Assay—
Transfer to a 250-mL volumetric flask an accurately measured volume of Oral Suspension, equivalent to about 250 mg of chlorothiazide, dilute with sodium hydroxide solution (1 in 250) to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, add dilute hydrochloric acid (1 in 100) to volume, and mix. Transfer 50.0 mL of the resulting solution to a 125-mL separator, and wash with two 25-mL portions of chloroform, discarding the washings. Transfer 10.0 mL of the washed solution to a 100-mL volumetric flask, dilute with sodium hydroxide solution (1 in 250) to volume, and mix. Dissolve an accurately weighed quantity of
USP Chlorothiazide RS in sodium hydroxide solution (1 in 250) to obtain a Standard solution having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 292 nm, with a suitable spectrophotometer, using sodium hydroxide solution (1 in 250) as the blank. Calculate the quantity, in mg, of chlorothiazide (C
7H
6ClN
3O
4S
2) in each mL of the Oral Suspension taken by the formula:
25(C/V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Chlorothiazide RS in the Standard solution;
V is the volume, in mL, of Oral Suspension taken; and
AU and
AS are the absorbances of the solution from the Oral Suspension and the Standard solution, respectively.
905
—