Potassium Guaiacolsulfonate

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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C₇H₇KO₅S·½H₂O 251.30

Benzenesulfonic acid, hydroxymethoxy-, monopotassium salt, hemihydrate;

Potassium hydroxymethoxybenzenesulfonate hemihydrate CAS RN^®: 78247-49-1; UNII: TTK33Z47F1.

Anhydrous 242.30

1 DEFINITION

Potassium Guaiacolsulfonate contains NLT 98.0% and NMT 102.0% of potassium guaiacolsulfonate (C₇H₇KO₅S), calculated on the anhydrous basis.

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197M

Analytical wavelength: 7-13 µm

Analysis: Dry at 105° for 18 h.

Acceptance criteria: Meets the requirements

B. SPECTROSCOPIC IDENTIFICATION TESTS (197), Ultraviolet-Visible Spectroscopy: 197U

Solution: 50 µg/mL, prepared as directed in the Assay

Acceptance criteria: Meets the requirements

C. IDENTIFICATION TESTS-GENERAL (191), Chemical Identification Tests, Potassium

Sample: A 1 in 10 solution

Acceptance criteria: Meets the requirements

3 ASSAY

3.1 PROCEDURE

Sample stock solution: Transfer about Img of Potassium Guaiacolsulfonate to a 500-mL volumetric flask. Dissolve in 400 mL of water, dilute with water to volume, and mix.

Sample solution: Dilute 10.0 mL of Sample stock solution with pH 7.0 phosphate buffer to 100.0 mL, and mix.

Standard solution: About 50 µg/mL of USP Potassium Guaiacolsulfonate RS in the same diluent used for the Sample solution

Instrumental conditions

Mode: UV

Analytical wavelength: Maximum absorbance at about 279 nm

Cell: 1 cm

Blank: A 1 in 10 mixture of water and pH 7.0 phosphate buffer

3.2 Analysis

Samples: Sample solution and Standard solution

Concomitantly determine the absorbances of the Sample solution and Standard solution, and calculate the percentage of potassium guaiacolsulfonate (C₇H₇KO₅S) in the portion of Potassium Guaiacolsulfonate taken:

Result = (A_U/A_S) x (C_S/C_U) x 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of USP Potassium Guaiacolsulfonate RS in the Standard solution (µg/mL)

C_U = concentration of Potassium Guaiacolsulfonate in the Sample solution (µg/mL)

Acceptance criteria: 98.0%-102.0% on the anhydrous basis

4 IMPURITIES

Delete the following:

4.1 SELENIUM (291)

0.003% (USP 1-May-2022)

4.2 SULFATE

Analysis: To 10 mL of a solution (1 in 20) add 5 drops of barium chloride TS, and acidify with hydrochloric acid.

Acceptance criteria: No turbidity is produced in 1 min.

5 SPECIFIC TESTS

WATER DETERMINATION (921), Method I: 3.0%-6.0%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in well-closed, light-resistant containers.

6.2 USP REFERENCE STANDARDS (11)

USP Potassium Guaiacolsulfonate RS