Potassium Bitartrate

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₄H₅KO₆       188.18

Butanedioic acid 2,3-dihydroxy-, [R-(R*,R*)]-, monopotassium salt;

Potassium hydrogen tartrate CAS RN®: 868-14-4; UNII: NPT6P8P3UU.

1 DEFINITION

Potassium Bitartrate, dried at 105° for 3 h, contains NLT 99.0% and NMT 101.0% of C₄H₅KO₆. 

2 IDENTIFICATION

A. Ignite it: it leaves a residue that imparts a reddish purple color to a nonluminous flame.

B. A saturated solution of it yields a yellowish orange precipitate with sodium cobaltinitrite TS.

C. Identification Tests—General, Tartrate〈191〉: Meets the requirements

3 ASSAY

Procedure

Sample: Dry 6 g of Potassium Bitartrate at 105° for 3 h. Allow to cool, and weigh.

Analysis: Dissolve the Sample in 100 mL of boiling water, add a few drops of phenolphthalein TS, and titrate with 1 N sodium hydroxide VS to a pink endpoint. Perform a blank determination (see Titrimetry 〈541〉). Each mL of 1 N sodium hydroxide is equivalent to 188.2 mg of C₄H₅KO₆.

Acceptance criteria: 99.0%–101.0% on the previously dried basis

4 IMPURITIES

4.1 Insoluble Matter

Sample: 500 mg

Analysis: Mix the Sample with 3 mL of 6 N ammonium hydroxide.

Acceptance criteria: No undissolved residue remains.

4.2 Limit of Ammonia

Sodium hypochlorite solution: Use a commercially available solution that contains 4.0%–6.0% of sodium hypochlorite. Oxidizing solution: [Note—Prepare on the day of use.] Alkaline sodium citrate TS and Sodium hypochlorite solution (4:1) Diluted sodium nitroferricyanide solution: Sodium nitroferricyanide TS and water (1:10)

Standard stock solution: Dry 300 mg of ammonium chloride over silica gel for 4 h, and use it to prepare a 0.3 mg/mL solution in water. This solution contains 100 µg/mL of ammonia.

Standard solution: 0.25 µg/mL of ammonia in water, from Standard stock solution

Sample solution: 2.5 mg/mL of Potassium Bitartrate in water. Heat gently to facilitate the dissolution.

Analysis

[Note—Carefully follow the order of addition stated below.]

Separately transfer 6.0 mL each of the Standard solution and the Sample solution to two color-comparison tubes. To each tube add 0.4 mL of phenol TS, 0.4 mL of Diluted sodium nitroferricyanide solution, and 1.0 mL of Oxidizing solution. Dilute with water to 10 mL, mix, and allow to stand for 1 h.

Acceptance criteria: The color of the Sample solution is not darker than the color of the Standard solution (NMT 0.01%).

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.