Polyoxyl Stearyl Ether
(pol'' ee ox' il steer' il ee' ther).

Polyethylene glycol monostearyl ether    
CH3(CH2)17(OCH2CH2)nOH, n = 2–20 [9005-00-9].
Polyoxyl Stearyl Ether is a mixture of the monostearyl ethers of mixed polyethylene glycols, the average polymer length being equivalent to NLT 2 and NMT 20 oxyethylene units (nominal value). It may contain various amounts of free stearyl alcohol and some free polyethylene glycol.
•  A. Infrared Absorption 197F: Use a thin film of melted Polyoxyl Stearyl Ether.
•  B. Procedure
Sample:  0.1 g
Analysis:  Dissolve or disperse the Sample in alcohol. Add 10 mL of diluted hydrochloric acid, 5 mL of barium chloride TS, and 10 mL of phosphomolybdic acid solution (1 in 10).
Acceptance criteria:  A precipitate is formed.
•  C. It meets the requirements in the test for Fats and Fixed Oils, Hydroxyl Value 401.
Organic Impurities 
•  Procedure: Limit of Free Ethylene Oxide and Dioxane
Analysis:  Proceed as directed in Ethylene Oxide and Dioxane 228, Method I.
Acceptance criteria 
Ethylene oxide:  NMT 1 µg/g (ppm)
Dioxane:  NMT 10 µg/g (ppm)
•  Fats and Fixed Oils, Acid Value 401: NMT 1.0, determined on 5.0 g
•  Fats and Fixed Oils, Hydroxyl Value 401: Within the ranges specified in the table below
Oxyethylene Units/Molecule
(Nominal Value)
Hydroxyl Value
2 150–180
10 75–90
20 40–60
•  Fats and Fixed Oils, Saponification Value 401: NMT 3.0, determined on 10.0 g
•  Alkalinity
Sample:  2.0 g of Polyoxyl Stearyl Ether
Analysis:  Dissolve the Sample to a hot mixture of 10 mL of alcohol and 10 mL of water. Add 0.05 mL of bromothymol blue TS. Titrate with 0.1 N hydrochloric acid to a yellow endpoint.
Acceptance criteria:  NMT 0.5 mL of 0.1 N hydrochloric acid is required.
•  Appearance of Solution: 5.0 g of Polyoxyl Stearyl Ether in 50.0 mL of alcohol. The solution is not more intensely colored than a solution prepared immediately before use by mixing 12.0 mL of ferric chloride CS, 5.0 mL of cobaltous chloride CS, and 2.0 mL of cupric sulfate CS with dilute hydrochloric acid (10 g/L) to make 50.0 mL, and diluting 12.5 mL of this solution with dilute hydrochloric acid (10 g/L) to make 100.0 mL. Make the comparison by viewing the substance and the solution downward in matched color-comparison tubes against a white surface (see Color and Achromicity 631).
•  Packaging and Storage: Preserve in tight containers, and store in a cool, dry place.
•  Labeling: Label it to indicate the average nominal number of oxyethylene units.
•  USP Reference Standards 11
USP Polyoxyl 2 Stearyl Ether RS
USP Polyoxyl 10 Stearyl Ether RS
USP Polyoxyl 20 Stearyl Ether RS
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
USP35–NF30 Page 1918
Pharmacopeial Forum: Volume No. 35(6) Page 1504