Packaging and storage— Preserve in tight containers.

USP Reference standards á11ñ— USP Chlorothiazide RS.

Identification— The UVabsorption spectrum of the solution of chlorothiazide prepared from Oral Suspension as directed in the Assayexhibits maxima and minima at the same wavelengths as that of a solution of USP Chlorothiazide RS,prepared as directed in the Assay,concomitantly measured.

Uniformity of dosage units á905ñ—

Deliverable volume á698ñ—

pHá791ñ: between 3.2and 4.0.

Assay— Transfer to a 250-mLvolumetric flask an accurately measured volume of Oral Suspension,equivalent to about 250mg of chlorothiazide,dilute with sodium hydroxide solution (1in 250)to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,add dilute hydrochloric acid (1in 100)to volume,and mix.Transfer 50.0mLof the resulting solution to a 125-mLseparator,and wash with two 25-mLportions of chloroform,discarding the washings.Transfer 10.0mLof the washed solution to a 100-mLvolumetric flask,dilute with sodium hydroxide solution (1in 250)to volume,and mix.Dissolve an accurately weighed quantity of USP Chlorothiazide RSin sodium hydroxide solution (1in 250)to obtain a Standard solution having a known concentration of about 10µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 292nm,with a suitable spectrophotometer,using sodium hydroxide solution (1in 250)as the blank.Calculate the quantity,in mg,of chlorothiazide (C7H6ClN3O4S2)in each mLof the Oral Suspension taken by the formula: in which Cis the concentration,in µg per mL,of USP Chlorothiazide RSin the Standard solution;Vis the volume,in mL,of Oral Suspension taken;and AUand ASare the absorbances of the solution from the Oral Suspension and the Standard solution,respectively.

Expert Committee:(PA5)Pharmaceutical Analysis 5

USP28–NF23Page 446

Phone Number:1-301-816-8305