Dimethyl Sulfoxide
78.13Methane, sulfinylbis-.
Methyl sulfoxide
[67-68-5].
Change to read:
» Dimethyl Sulfoxide contains not less than 99.9 percent of C2H6OS, 
calculated on the anhydrous basis.USP32
calculated on the anhydrous basis.USP32
Packaging and storage—
Preserve in tight, light-resistant containers.
Identification—
A:
Infrared Absorption 
197F
, potassium bromide plates being used.
197F, potassium bromide plates being used.
B:
Add 1.5 mL cautiously and dropwise to 2.5 mL of hydriodic acid in a test tube cooled in ice. Filter the mixture rapidly, and collect the precipitate. Dry the precipitate in vacuum: a deep violet, crystalline solid is obtained, and it is soluble in chloroform, yielding a red solution.
Specific gravity 841:
between 1.095 and 1.101.
841:
between 1.095 and 1.101.
Delete the following:
Congealing temperature 651:
not less than 18.3
, indicating not less than 99.9% of C2H6OS.USP32
Refractive index 831:
between 1.4755 and 1.4775.
831:
between 1.4755 and 1.4775.
Acidity—
Dissolve 50.0 g in 100 mL of water, and add phenolphthalein TS. If the solution remains colorless, titrate with 0.01 N sodium hydroxide until a pink color appears: not more than 5.0 mL of 0.01 N sodium hydroxide is consumed.
Water, Method I 921:
not more than 0.1%. [note—Weigh and transfer the test specimen in an environment of low humidity to minimize absorption of atmospheric water.]
921:
not more than 0.1%. [note—Weigh and transfer the test specimen in an environment of low humidity to minimize absorption of atmospheric water.]
Ultraviolet absorbance—
Maintain Dimethyl Sulfoxide in a water bath at a temperature of less than 20 [note—Do not freeze.], and purge with dry nitrogen for 30 minutes. Record the UV absorption spectrum between 270 and 350 nm in a 1-cm cell, using water as the blank: the spectrum is smooth with no absorption maxima; the absorbance at 275 nm is not more than 0.20, and the absorbance ratios, A285/A275 and A295/A275, at the wavelengths indicated by the subscripts, are not more than 0.65 and 0.45, respectively.
[note—Do not freeze.], and purge with dry nitrogen for 30 minutes. Record the UV absorption spectrum between 270 and 350 nm in a 1-cm cell, using water as the blank: the spectrum is smooth with no absorption maxima; the absorbance at 275 nm is not more than 0.20, and the absorbance ratios, A285/A275 and A295/A275, at the wavelengths indicated by the subscripts, are not more than 0.65 and 0.45, respectively.
Delete the following:
Substances darkened by potassium hydroxide—
Add 0.5 mL of water and 1.0 g of solid potassium hydroxide to 25 mL of Dimethyl Sulfoxide in a glass-stoppered, 50-mL flask. [note—Use only solid potassium hydroxide that is white with no discoloration.] Insert the stopper, and heat in a steam cone for 20 minutes. Cool to room temperature: the absorbance of the solution at 350 nm, measured in a 2-cm cell, water being used as the blank, does not exceed 0.046.USP32
Delete the following:
Limit of dimethyl sulfone—
System suitability solution—
Prepare a solution containing about 0.15 mg of dimethyl sulfone per mL and 0.1 mg of dibenzyl per mL in Dimethyl Sulfoxide.
Chromatographic system—
The gas chromatograph is equipped with a flame-ionization detector and a suitable recorder, and contains a 3-mm × 1.5-m column packed with 10% liquid phase G25 on support S1A (see Chromatography 621). The column temperature is programmed to change at a rate of about 10 per minute from 100 to 170, the injection port is maintained at a temperature of about 210, and the detector block is maintained at a temperature of about 220. Helium is used as the carrier gas, flowing at the rate of about 30 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the column efficiency as determined from the dimethyl sulfoxide peak is not less than 1000 theoretical plates; and the resolution, R, between the dimethyl sulfone and dibenzyl peaks is not less than 5.0.
621). The column temperature is programmed to change at a rate of about 10 per minute from 100 to 170, the injection port is maintained at a temperature of about 210, and the detector block is maintained at a temperature of about 220. Helium is used as the carrier gas, flowing at the rate of about 30 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the column efficiency as determined from the dimethyl sulfoxide peak is not less than 1000 theoretical plates; and the resolution, R, between the dimethyl sulfone and dibenzyl peaks is not less than 5.0.
Procedure—
Inject about 1 µL of Dimethyl Sulfoxide into the gas chromatograph, record the chromatograms, and measure the responses of the peaks: the response of any peak, other than that of dimethyl sulfoxide, is not greater than 0.03% of the total of the responses of all of the peaks; and the total of the responses of all secondary peaks is not greater than 0.1% of the total of the responses of all of the peaks.USP32
USP32
Change to read:
Limit of nonvolatile residue—
Evaporate about 100.0 g to dryness in a tared, preconditioned dish on a hot plate under a suitable fume hood. Evaporate gently so boiling does not occur. The weight of the residue does not exceed 0.01%.USP32
Add the following:
Related compounds—
System suitability solution
—Prepare a solution containing about 0.15 mg of dimethyl sulfone per mL and 0.1 mg of dibenzyl per mL in Dimethyl Sulfoxide.
Chromatographic system
(see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector and contains a 0.32-mm × 15-m column bonded with a 3-µm film of phase G2. The column temperature is programmed to change from 100 to 170 at a rate of about 10 per minute, the injection port is maintained at a temperature of about 210, and the detector block is maintained at a temperature of about 220. Helium is used as the carrier gas, flowing at a rate of 1.7 mL per minute, and the split ratio is 33:1. [Note—The split ratio can be modified in order to optimize performance.] Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between dimethyl sulfone and dibenzyl is not less than 5.0; and the column efficiency, determined from the dimethyl sulfoxide peak, is not less than 1000 theoretical plates.
621)—The gas chromatograph is equipped with a flame-ionization detector and contains a 0.32-mm × 15-m column bonded with a 3-µm film of phase G2. The column temperature is programmed to change from 100 to 170 at a rate of about 10 per minute, the injection port is maintained at a temperature of about 210, and the detector block is maintained at a temperature of about 220. Helium is used as the carrier gas, flowing at a rate of 1.7 mL per minute, and the split ratio is 33:1. [Note—The split ratio can be modified in order to optimize performance.] Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between dimethyl sulfone and dibenzyl is not less than 5.0; and the column efficiency, determined from the dimethyl sulfoxide peak, is not less than 1000 theoretical plates.
Procedure—
Inject about 1 µL of Dimethyl Sulfoxide into the gas chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of total impurities in the portion of Dimethyl Sulfoxide taken by the formula:
USP32
100(rU / rs)
in which rU is the sum of the areas of all the impurity peaks; and rs is the sum of the areas of all the peaks: not more than 0.1% of total impurities is found.USP32
Add the following:
Assay—
Using the results from the test for Limit of nonvolatile residue and the test for Related compounds, calculate the percentage of C2H6OS in the portion of Dimethyl Sulfoxide taken by subtracting the percentage of nonvolatile residue and the percentage of total impurities found from 100.0%. [Note—A correction for percent water is not applied to the result.]USP32
Auxiliary Information—
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Chromatographic Column—
| Topic/Question | Contact | Expert Committee |
| Monograph | Feiwen Mao, M.S.
Scientist 1-301-816-8320 |
(MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals |
| Reference Standards | Lili Wang, Technical Services Scientist 1-301-816-8129 RSTech@usp.org |
USP32–NF27 Page 2168
Pharmacopeial Forum: Volume No. 34(1) Page 88
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.