Mineral Oil
» Mineral Oil is a purified mixture of liquid hydrocarbons obtained from petroleum. It may contain a suitable stabilizer.
Packaging and storage— Preserve in tight, light-resistant containers. No storage requirements specified.
Labeling— Label it to indicate the name and quantity of any substance added as a stabilizer.
A: Infrared Absorption 197F.
B: It meets the requirements of the test for Viscosity.
Specific gravity 841: between 0.845 and 0.905.
Viscosity 911 Perform the test at 40.0 ± 0.1, using a suitable capillary viscometer: the kinematic viscosity is between 34.5 and 150.0 mm2·s-1.
Acidity— Add 20 mL of boiling water to 10 mL of Mineral Oil, and shake vigorously for about 1 minute. Allow to cool, and draw off the separated water. To 10 mL of the filtrated aqueous layer add 0.1 mL of phenolphthalein TS: the solution does not produce a pink color. Not more than 1.0 mL of 0.01 N sodium hydroxide is required to change the color to pink.
Readily carbonizable substances— Place 5 mL in a glass-stoppered test tube that previously has been rinsed with hot nitric acid (see Cleaning Glass Apparatus 1051), then rinsed with water, and dried. Add 5 mL of sulfuric acid containing from 94.5% to 94.9% of H2SO4, and heat in a boiling water bath for 10 minutes. After the test tube has been in the bath for 30 seconds, remove it quickly, and, while holding the stopper in place, give three vigorous, vertical shakes over an amplitude of about 5 inches. Repeat every 30 seconds. Do not keep the test tube out of the bath longer than 3 seconds for each shaking period. At the end of 10 minutes from the time when first placed in the water bath, remove the test tube: the Oil may turn hazy, but it remains colorless or shows a slight pink or yellow color, and the acid does not become darker than the standard color produced by mixing in a similar test tube 3 mL of ferric chloride CS, 1.5 mL of cobaltous chloride CS, and 0.5 mL of cupric sulfate CS, this mixture being overlaid with 5 mL of Oil (see Readily Carbonizable Substances Test 271).
Limit of polycyclic aromatic hydrocarbons—
Dimethyl sulfoxide— Use spectrophotometric grade dimethyl sulfoxide.
Standard solution— Dissolve a quantity of USP Naphthalene RS, accurately weighed, in 2,2,4-trimethylpentane (isooctane), and dilute quantitatively and stepwise with 2,2,4-trimethylpentane to obtain a solution having a concentration of 7.0 µg per mL. Determine the absorbance of this solution in a 1-cm cell at the wavelength of maximum absorbance at about 275 nm, using 2,2,4-trimethylpentane as the blank.
Procedure— Transfer 25.0 mL of Mineral Oil and 25 mL of n-hexane to a 125-mL separator, and mix. [note—Use only n-hexane that previously has been washed by being shaken twice with one-fifth its volume of Dimethyl sulfoxide. Use no lubricants other than water on the stopcock, or use a separator equipped with a suitable polymeric stopcock.] Add 5.0 mL of Dimethyl sulfoxide, and shake the mixture vigorously for 1 minute. Allow to stand until the lower layer is clear, transfer the lower layer to another 125-mL separator, add 2 mL of n-hexane, and shake vigorously. Separate the lower layer, and determine its absorbance in a 1-cm cell, in the range of 260 nm to 350 nm, using as the blank Dimethyl sulfoxide that previously has been shaken vigorously for 1 minute with n-hexane in the ratio of 5 mL of Dimethyl sulfoxide and 25 mL of n-hexane. The absorbance at any wavelength in the specified range is not greater than one-third of the absorbance, at 275 nm, of the Standard solution.
Solid paraffin— Fill a tall, cylindrical, standard oil-sample bottle of colorless glass of about 120-mL capacity with Mineral Oil that has been dried previously in a beaker at 105 for 2 hours and cooled to room temperature in a desiccator over silica gel. Insert the stopper, and immerse the bottle in a mixture of ice and water for 4 hours: the test specimen is sufficiently clear that a black line 0.5 mm in width, on a white background, held vertically behind the bottle, is clearly visible.
Limit of sulfur compounds— Prepare a saturated solution of lead (II) oxide in sodium hydroxide solution (1 in 5), and mix 2 drops of the clear saturated solution with 4.0 mL of Mineral Oil and 2 mL of dehydrated alcohol. Heat the mixture at 70 for 10 minutes with frequent shaking, and cool. No dark brown color develops.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Hong Wang, Ph.D.
(EM205) Excipient Monographs 2
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2984
Pharmacopeial Forum: Volume No. 33(5) Page 962