Rubbing Alcohol

» Rubbing Alcohol and all preparations under the classification of Rubbing Alcohols are manufactured in accordance with the requirements of the U.S. Treasury Department, Bureau of Alcohol, Tobacco, and Firearms, Formula 23-H (8 parts by volume of acetone, 1.5 parts by volume of methyl isobutyl ketone, and 100 parts by volume of ethyl alcohol) being used. It contains not less than 68.5 percent and not more than 71.5 percent by volume of dehydrated alcohol, the remainder consisting of water and the denaturants, with or without color additives, and perfume oils. Rubbing Alcohol contains, in each 100 mL, not less than 355 mg of sucrose octaacetate or not less than 1.40 mg of denatonium benzoate. The preparation may be colored with one or more color additives, listed by the FDA for use in drugs. A suitable stabilizer may be added. Rubbing Alcohol complies with the requirements of the Bureau of Alcohol, Tobacco, and Firearms of the U.S. Treasury Department.

[note—Rubbing Alcohol is packaged, labeled, and sold in accordance with the regulations issued by the U.S. Treasury Department, Bureau of Alcohol, Tobacco, and Firearms. ]

Packaging and storage— Preserve in tight containers, remote from fire, and store at controlled room temperature.

Labeling— Label it to indicate that it is flammable.

USP Reference standards

—

USP Denatonium Benzoate RS

Specific gravity

841

: between 0.8691 and 0.8771 at 15.56

(the U.S. Government standard temperature for alcohol determination), for Rubbing Alcohol manufactured with specially denatured alcohol Formula 23-H.

Limit of nonvolatile residue—

Where the denaturant is denatonium benzoate— Evaporate 200.0 mL of Rubbing Alcohol, transferred in convenient portions, in a suitable tared dish on a steam bath, and dry the residue at 105

for 1 hour: the weight of the residue is not less than 2.8 mg. (Retain the residue for the Assay for denatonium benzoate.)

Where the denaturant is sucrose octaacetate— Evaporate 25.0 mL of Rubbing Alcohol in a suitable tared dish on a steam bath, and dry the residue at 105

for 1 hour: the weight of the residue is not less than 89 mg. (Retain the residue for the Assay for sucrose octaacetate.)

Methanol— Dilute 0.50 mL of it with water to 1.0 mL. To 0.50 mL of the resulting solution add 1 drop of dilute phosphoric acid (1 in 20) and 1 drop of potassium permanganate solution (1 in 20). Mix, allow to stand for 1 minute, and add sodium metabisulfite solution (1 in 20), dropwise, until the permanganate color is discharged. If a brown color remains, add 1 drop of dilute phosphoric acid (1 in 20). To the colorless solution add 5 mL of freshly prepared chromotropic acid TS, and heat in a water bath at 60

for 10 minutes: no violet color appears.

Assay for denatonium benzoate—

Buffer solution— Dissolve 9.23 g of anhydrous dibasic sodium phosphate in 800 mL of water, adjust with saturated citric acid solution to a pH of 4 ± 0.1, dilute with water to 1000 mL, and mix.

Standard preparation— Dissolve about 25 mg of USP Denatonium Benzoate RS, accurately weighed, in water to make 500 mL, and mix.

Assay preparation— Dissolve the residue obtained in the test for Limit of nonvolatile residue in 50.0 mL of water, and transfer to a suitable flask.

Procedure— Treat the Standard preparation, Assay preparation, and blank similarly and concomitantly. Transfer 10.0 mL each of the Standard preparation, Assay preparation, and Buffer solution to individual 250-mL separators, and add to each 40 mL of Buffer solution, 10 mL of a 1 in 1000 solution of bromophenol blue in chloroform, and 60 mL of chloroform. Shake the separators vigorously for 2 minutes, allow to stand for 15 minutes, then withdraw the chloroform layers through chloroform-washed cotton into 100-mL volumetric flasks. Repeat the extraction with 20 mL of chloroform, adding the filtered chloroform extracts to the respective volumetric flasks, dilute with chloroform to volume, and mix. Without delay, concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 410 nm, with a suitable spectrophotometer, using the blank to set the instrument. Calculate the quantity, in mg, of denatonium benzoate (C28H34N2O3·H2O) in 100 mL of Rubbing Alcohol taken by the formula:

0.025C(AU / AS)

in which C is the concentration, in µg per mL, of USP Denatonium Benzoate RS in the Standard preparation; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.

Assay for sucrose octaacetate— Using about 50 mL of 70% alcohol, transfer the residue obtained in the test for Limit of nonvolatile residue to a 500-mL conical flask. Neutralize the solution with 0.1 N sodium hydroxide VS, using phenolphthalein TS as the indicator. Add 25.0 mL of 0.1 N sodium hydroxide, attach an air condenser to the flask, and reflux on a steam bath for 1 hour. Remove from the steam bath, cool quickly, and titrate the excess alkali with 0.1 N sulfuric acid VS, using phenolphthalein TS as the indicator. Perform a blank determination (see Residual Titrations under Titrimetry

541

). Each mL of 0.1 N sodium hydroxide is equivalent to 8.483 mg of sucrose octaacetate (C28H38O19).

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Clydewyn M. Anthony, Ph.D. Senior Scientific Liaison 1-301-816-8139	(SM22010) Monographs - Small Molecules 2
Reference Standards	RS Technical Services 1-301-816-8129 rstech@usp.org

USP35–NF30 Page 2092

Pharmacopeial Forum: Volume No. 27(3) Page 2507