AOAC Official Method 974.41 Polythiazide in Drugs
Spectrophotometric Method
First Action 1974
Final Action 1976
(Applicable to formulations containing vanillin.)
A. Principle
Vanillin, which interferes in method, is condensed through aldehyde group with primary amine group of sulfanilic acid to form strongly polar and H2O-soluble Schiff’s base, which is retained in aqueous immobile phase of column. Less polar polythiazide is eluted with mobile phase, ether-isooctane, and determined by UV spectrophotometry.
B. Apparatus and Reagent
(Use H2O-washed solvents throughout.)
(a) Chromatographic tube and tamping rod.—See 967.31A (see 19.1.02).
(b) Diatomaceous earth.—See 960.53B (see 18.1.01).
(c) Dilute ammonium hydroxide.—1M. Dilute 17 mL NH4OH to 250 mL with H2O.
(d) Ammonium sulfanilate solution.—6%. Dissolve 6.0 g sulfanilic acid in1MNH4OHand dilute to 100mLwith1MNH4OH.
(e) Polythiazide standard solution.—10 mg/mL. Accurately weigh ca 100 mgUSP polythiazide Reference Standard, transfer to 100 mL volumetric flask, and dilute to volume with methanol. Further dilute 10 mL of this solution to 100 mL with methanol and 10 mL diluted solution to 100 mL with methanol.
C. Preparation of Test Portion
Accurately weigh test portion containing ca 1 mg polythiazide and transfer to 150 mL beaker. Add 0.25 mL dimethylsulfoxide (DMSO) and mix thoroughly to wet entire test sample. Let stand 3–4 min.
