Methylsulfonylmethane
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C2H6O2S94.13
Dimethyl sulfone;    
Sulfonylbismethane    [67-71-0].
DEFINITION
Methylsulfonylmethane contains NLT 98.0% and NMT 102.0% of methylsulfonylmethane (C2H6O2S), calculated on the anhydrous basis. The chromatographic purity is NLT 99.8%.
IDENTIFICATION
•  B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
ASSAY
•  Procedure
Diluent: Transfer 950 mL of methanol to a 1-L volumetric flask. Add 0.60 mL of di(ethylene glycol) methyl ether, and dilute with methanol to volume.
Standard solution: 0.4 mg/mL of USP Methylsulfonylmethane RS in Diluent. Sonicate at 50 for 1 min, and allow to cool to room temperature.
Sample solution: 0.4 mg/mL of Methylsulfonylmethane in Diluent. Sonicate at 50 for 1 min, and allow to cool to room temperature.
Chromatographic system 
Mode: GC
Detector: Flame ionization
Column: 0.53-mm × 30-m capillary column coated with a 5-µm phase G2
Temperature 
Column: 120
Injector: 250
Detector: 250
Carrier gas: Helium
Flow rate: 5 mL/min
Split ratio: 2:1
Injection size: 1 µL
System suitability 
Sample: Standard solution
Suitability requirements 
Relative standard deviation: NMT 2.0% for the peak response ratio of methylsulfonylmethane to di(ethylene glycol) methyl ether from replicate injections
Analysis 
Samples: Standard solution and Sample solution
Calculate the percentage of methylsulfonylmethane (C2H6O2S) in the portion of Methylsulfonylmethane taken:
Result = (RU/RS) × (CS/CU) × 100
RU== peak response ratio of methylsulfonylmethane to di(ethylene glycol) methyl ether from the Sample solution
RS== peak response ratio of methylsulfonylmethane to di(ethylene glycol) methyl ether from the Standard solution
CS== concentration of USP Methylsulfonylmethane RS in the Standard solution (mg/mL)
CU== concentration of Methylsulfonylmethane in the Sample solution (mg/mL)
Acceptance criteria: 98.0%–102.0% on the anhydrous basis
IMPURITIES
•  Heavy Metals, Method I 231: NMT 3 µg/g
•  Chromatographic Purity and Limit of Dimethyl Sulfoxide
Standard stock solution: 1.0 mg/mL of USP Dimethyl Sulfoxide RS in methanol
Sensitivity check solution: 2.0 µg/mL from the Standard stock solution in methanol
System suitability solution:  0.1 mg/mL of USP Dimethyl Sulfoxide RS and 0.4 mg/mL of USP Methylsulfonylmethane RS in methanol. In a 50-mL volumetric flask dissolve 20 mg of USP Methylsulfonylmethane RS in 5 mL of the Standard stock solution, and dilute with methanol to volume.
Sample solution: 2 mg/mL of Methylsulfonylmethane in methanol. Sonicate at 50 for 1 min, and allow to cool to room temperature.
Chromatographic system: Proceed as directed in the Assay.
System suitability 
Samples: Sensitivity check solution and System suitability solution
Suitability requirements 
Signal-to-noise ratio: NLT 10 for dimethyl sulfoxide peak, Sensitivity check solution
Resolution: NLT 2.0 between dimethyl sulfoxide and methylsulfonylmethane, System suitability solution
Analysis 
Sample: Sample solution
Calculate the percentage of each impurity in the portion of Methylsulfonylmethane taken:
Result = (rU/rT) × 100
rU== response of each impurity in the Sample solution
rT== sum of the responses of all of the peaks other than the solvent peak
Acceptance criteria 
Individual impurities: NMT 0.1% of dimethyl sulfoxide; NMT 0.05% of any other individual impurity
Total impurities: NMT 0.2% for all impurities, including dimethyl sulfoxide
SPECIFIC TESTS
•  Melting Range or Temperature 741: 108.5–110.5
•  Microbial Enumeration Tests 2021: The total aerobic microbial count is NMT 103 cfu/g or mL, and the total combined molds and yeasts count is NMT 102 cfu/g or mL.
•  Absence of Specified Microorganisms 2022: It meets the requirements for absence of Escherichia coli in 10 g.
•  Water Determination, Method I 921: NMT 0.1%. [Note—500 mg of methylsulfonylmethane may be required for this analysis. ]
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in well-closed containers.
•  USP Reference Standards 11
USP Dimethyl Sulfoxide RS Click to View Structure
USP Methylsulfonylmethane RS
Dimethyl sulfone.
    C2H6O2S        94.13
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USP35–NF30 Page 1383
Pharmacopeial Forum: Volume No. 32(3) Page 826
Chromatographic Column— 
Chromatographic columns text is not derived from, and not part of, USP 35 or NF 30.