Potassium Guaiacolsulfonate
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C7H7KO5S·½H2O 251.30

Benzenesulfonic acid, hydroxymethoxy-, monopotassium salt, hemihydrate.
Potassium hydroxymethoxybenzenesulfonate hemihydrate [78247-49-1].

Anhydrous 242.30
» Potassium Guaiacolsulfonate contains not less than 98.0 percent and not more than 102.0 percent of C7H7KO5S, calculated on the anhydrous basis.
Packaging and storage— Preserve in well-closed, light-resistant containers.
A: Infrared Absorption 197M: between 7 µm and 13 µm, previously dried at 105 for 18 hours.
Solution: 50 µg per mL, prepared as directed in the Assay.
C: A solution (1 in 10) responds to the tests for Potassium 191.
Water, Method I 921: between 3.0% and 6.0%.
Selenium 291: 0.003%.
Sulfate— To 10 mL of a solution (1 in 20) add 5 drops of barium chloride TS, and acidify with hydrochloric acid: no turbidity is produced in 1 minute.
Heavy metals 231 Dissolve 1.0 g in 1 mL of 1 N acetic acid, and dilute with water to 25 mL. The limit is 0.002%.
Assay— Transfer about 250 mg of Potassium Guaiacolsulfonate, accurately weighed, to a 500-mL volumetric flask, dissolve in 400 mL of water, dilute with water to volume, and mix. Dilute 10.0 mL of this solution with pH 7.0 phosphate buffer to 100.0 mL, and mix. Concomitantly determine the absorbances of this solution and a Standard solution of USP Potassium Guaiacolsulfonate RS in the same medium, having a known concentration of about 50 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 279 nm, with a suitable spectrophotometer, using a 1 in 10 mixture of water and pH 7.0 phosphate buffer as the blank. Calculate the quantity, in mg, of C7H7KO5S in the Potassium Guaiacolsulfonate taken by the formula:
5C(AU / AS)
in which C is the concentration, in µg per mL, calculated on the anhydrous basis, of USP Potassium Guaiacolsulfonate RS in the Standard solution, and AU and AS are the absorbances of the preparation under assay and the Standard solution, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Clydewyn M. Anthony, Ph.D.
(MDCCA05) Monograph Development-Cough Cold and Analgesics
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 3348