AOAC Official Method 933.10 Hexylresorcinol in Drugs
Titrimetric Method
First Action 1933
Final Action
A. Reagents
(a) Sodium thiosulfate standard solution.—0.1M. Prepare as in 942.27A (see A.1.13).
(b) Purified methanol.—Purify if necessary as follows: Add enough Br2 to commercial methanol to give bright yellow solution, heat to bp onH2Obath, and boil 5 min. Cool, and carefully decolorize by adding 10% NaHSO3 solution dropwise until just colorless.
(c) Potassium bromide–bromate solution.—0.01667M. Prepare as in 947.13A (see A.1.08). Standardize as follows: Transfer 30 mL to iodine flask, and add 25 mL H2O, 5 mL 20% KI solution, and 5 mL HCl. Shake thoroughly and titrate with 0.1M Na2S2O3, using starch indicator (mix 2 g finely powdered potato starch with cold H2O to thin paste; add ca 200 mL boiling H2O, stirring constantly, and immediately discontinue heating; refrigerate. Prepare fresh at least weekly.).
