Tetramethylammonium Hydroxide Solution in Methanol
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
CAS RN®: 75-59-2.—A solution in methanol of tetramethylammonium hydroxide [(CH3)4NOH—91.15]. Is generally available in concentrations of 10% and 25%. The following specifications apply specifically to the 25% concentration; for other concentrations, appropriate adjustments in the procedures may be necessary.
Assay: Accurately weigh about 1 g of the solution, and dilute with water to about 50 mL. Add phenolphthalein TS, and titrate with 0.1 N hydrochloric acid VS to the disappearance of the pink color: each mL of 0.1 N hydrochloric acid VS is equivalent to 91.15 mg of (CH3)4NOH. Between 23% and 25% is found.
Clarity: A portion of it in a test tube is clear, or only slightly turbid, when viewed transversely.
