MonothioglycerolMonothioglycerol

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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C₃H₈O₂S 108.16 

1,2-Propanediol, 3-mercapto-; 

3-Mercapto-1,2-propanediol CAS RN®: 96-27-5. 

1 DEFINITION 

Monothioglycerol contains NLT 97.0% and NMT 101.0% of monothioglycerol (C₃H₈O₂S), calculated on the anhydrous basis

2 ASSAY 

Procedure 

Sample: 400 mg 

Titrimetric system (See Titrimetry 〈541〉.) Mode: Direct titration Titrant: 0.1 N iodine VS 

Endpoint detection: Visual 

Analysis: Dissolve the Sample in 50 mL of water. Titrate with Titrant, adding 3 mL of starch TS as the endpoint is approached. Each mL of Titrant is equivalent to 10.82 mg of monothioglycerol (C₃H₈O₂S). 

Acceptance criteria: 97.0%–101.0% on the anhydrous basis 

3 IMPURITIES 

Residue on Ignition 〈281〉: NMT 0.1% 

Change to read: 

Selenium 〈291〉, Procedures, Procedure 1 

Test solution: 200 µL 

Acceptance criteria: 30 µg/g 

4 SPECIFIC TESTS 

Specific Gravity 〈841〉: 1.241–1.250 

Refractive Index 〈831〉: 1.521–1.526 

pH 〈791〉 

Sample solution: 1 in 10 

Acceptance criteria: 3.5–7.0 

Water Determination, Method II 〈921〉: NMT 5.0% 

5 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers.