Stearyl Alcohol

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₁₈H₃₈O 270.50

1-Octadecanol;

Octadecan-1-ol CAS RN®: 112-92-5.

1 DEFINITION

Stearyl Alcohol contains NLT 90.0% and NMT 102.0% of stearyl alcohol (C₁₈H₃₈O), the remainder consisting chiefly of related alcohols. It is obtained from sources of vegetable, animal, or synthetic origin.

2 IDENTIFICATION

2.1 A. Chromatographic Identity

System suitability solution, Sample solution, and Analysis: Proceed as directed in the Assay.

Acceptance criteria: The retention time of the major peak of the Sample solution, excluding the solvent and internal standard peaks, corresponds to the stearyl alcohol peak of the System suitability solution.

3 ASSAY

[Note-If 1-pentadecanol is one of the related alcohols in stearyl alcohol derived from animal sources, the Assay and Organic Impurity Test 1, Limit of Related Fatty Alcohols are not suitable.]

3.1 Procedure

Internal standard solution: 1 mg/mL of 1-pentadecanol (internal standard) in ethanol

System suitability solution: Prepare 1 mg/mL each of USP Cetyl Alcohol RS, USP Stearyl Alcohol RS, and USP Oleyl Alcohol RS in Internal standard solution. Heat the solution in a sealed container in a 50° water bath until all fatty alcohols are dissolved. Allow the solution to cool to room temperature, and mix well.

Standard solution: Prepare 1.0 mg/mL of USP Stearyl Alcohol RS in Internal standard solution, and heat the solution in a sealed container in a 50° water bath until stearyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

Sample solution: Prepare 1.0 mg/mL of Stearyl Alcohol in Internal standard solution. Heat the solution in a sealed container in a 50° water bath until stearyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: GC
• Detector: Flame ionization
• Column: 0.25-mm × 30-m fused silica capillary; coated with a 0.25-µm layer of phase G7
• Temperatures
• Detector: 280°
• Injection port: 270°
• Column: See Table 1.

Table 1

• Carrier gas: Hydrogen
• Flow rate: 2.0 mL/min, constant flow mode
• Injection volume: 1 µL
• Injection type: Split, split ratio, 100:1
• Liner: Single taper, low pressure drop liner with deactivated wool
• Run time: 15 min

System suitability

• Samples: System suitability solution and Standard solution
• [Note-See Table 2 for the relative retention times.]

Table 2

• Suitability requirements
• Resolution: NLT 30 between the cetyl alcohol and stearyl alcohol peaks; NLT 2.0 between the stearyl and oleyl alcohol peaks, System suitability solution
• Tailing factor: 0.8–1.8 for the stearyl alcohol and 1-pentadecanol peaks, Standard solution
• Relative standard deviation: NMT 1%, using the area ratio of stearyl alcohol to 1-pentadecanol, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of stearyl alcohol (C₁₈H₃₈O) in the portion of Stearyl Alcohol taken:

Result = (Rᵤ/Rₛ) × (Cₛ/Cᵤ) × 100

Rᵤ = peak response ratio of stearyl alcohol to the internal standard from the Sample solution

Rₛ = peak response ratio of stearyl alcohol to the internal standard from the Standard solution

Cₛ = concentration of USP Stearyl Alcohol RS in the Standard solution (mg/mL)

Cᵤ = concentration of Stearyl Alcohol in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–102.0%

4 IMPURITIES

4.1 Residue on Ignition 〈281〉

NMT 0.1%, determined on 2 g

[Note-On the basis of the manufacturing route, perform either Organic Impurity Test 1 (vegetable or animal sources) or Organic Impurity Test 2 (synthetic sources).]

4.2 Organic Impurity Test 1, Limit of Related Fatty Alcohols

Solution A: 1 mg/mL of 1-pentadecanol in ethanol

Resolution solution: Prepare 1 mg/mL each of USP Lauryl Alcohol RS, USP Myristyl Alcohol RS, USP Cetyl Alcohol RS, USP Stearyl Alcohol RS, USP Oleyl Alcohol RS, USP Linolenyl Alcohol RS, and USP Arachidyl Alcohol RS in Solution A. Heat the solution in a sealed container in a 50° water bath until all fatty alcohols are dissolved. Allow the solution to cool to room temperature, and mix well. Dilute the solution with Ethanol to obtain a solution containing 0.05 mg/mL each of USP Lauryl Alcohol RS, USP Myristyl Alcohol RS, USP Cetyl Alcohol RS, 1-pentadecanol, USP Stearyl Alcohol RS, USP Oleyl Alcohol RS, USP Linolenyl Alcohol RS, and USP Arachidyl Alcohol RS.

Sample solution: 1 mg/mL of Stearyl Alcohol in ethanol. Heat the solution in a sealed container in a 50° water bath until stearyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

Chromatographic system: Proceed as directed in the Assay, except for the split ratio.

Injection type: Split; split ratio, 5:1

System suitability

• Sample: Resolution solution
• [Note-See Table 3 for the relative retention times.]

Table 3

ᵃ Related linear chain fatty alcohol.

ᵇ Internal standard.

ᶜ Sample.

• Suitability requirements
• Resolution: NLT 15 between the myristyl alcohol and 1-pentadecanol peaks; NLT 30 between the cetyl alcohol and stearyl alcohol peaks; NLT 2.0 between the stearyl and oleyl alcohol peaks

Analysis

Samples: Resolution solution and Sample solution

Identify each related fatty alcohol peak in the Sample solution based on those in the Resolution solution.

Calculate the percentage of each related fatty alcohol or any unidentified impurity in the portion of Stearyl Alcohol taken:

Result = (r_U/r_T) × 100

r_U = peak response of each related fatty alcohol (or any unidentified impurity) from the Sample solution

r_T = sum of all the peak responses excluding peak responses due to solvent from the Sample solution

Acceptance criteria: Disregard peaks that are less than 0.05% for any unidentified impurities, and any peaks due to solvent.

Sum of unidentified impurities: NMT 1%

Sum of related fatty alcohols and unidentified impurities: NMT 10.0%

4.3 Organic Impurity Test 2, Limit of Branched-Chain Fatty Alcohols, Related Linear Fatty Alcohols, and Related Unsaturated Alcohols and Alkanes

Solution A: 1 mg/mL of 1-pentadecanol in ethanol

Resolution solution: Prepare 1 mg/mL each of USP Lauryl Alcohol RS, USP Myristyl Alcohol RS, USP Cetyl Alcohol RS, USP Stearyl Alcohol RS, USP Oleyl Alcohol RS, USP Linolenyl Alcohol RS, and USP Arachidyl Alcohol RS in Solution A. Heat the solution in a sealed container in a 50° water bath until all fatty alcohols are dissolved. Allow the solution to cool to room temperature, and mix well. Dilute the solution with ethanol to obtain a solution containing 0.05 mg/mL each of USP Lauryl Alcohol RS, USP Myristyl Alcohol RS, USP Cetyl Alcohol RS, 1-pentadecanol, USP Stearyl Alcohol RS, USP Oleyl Alcohol RS, USP Linolenyl Alcohol RS, and USP Arachidyl Alcohol RS.

Sample solution: 1 mg/mL of Stearyl Alcohol in ethanol. Heat the solution in a sealed container in a 50° water bath until stearyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

Chromatographic system: Proceed as directed in the Assay, except for the split ratio.

Injection type: Split, split ratio, 5:1

System suitability

• Sample: Resolution solution
• [Note-See Table 4 for the relative retention times.]

Table 4

ᵃ Alkane.

ᵇ Related linear chain fatty alcohol.

ᶜ Internal standard.

ᵈ Linear secondary fatty alcohol.

ᵉ Related branched-chain fatty alcohol.

ᶠ Related unsaturated alcohol.

ᵍ Sample.

• Suitability requirements
• Resolution: NLT 15 between the myristyl alcohol and 1-pentadecanol peaks; NLT 30 between the cetyl alcohol and stearyl alcohol peaks; NLT 2.0 between the stearyl and oleyl alcohol peaks

Analysis

Samples: Resolution solution and Sample solution

Identify each related fatty alcohol, alkane, and unsaturated alcohol peak in the Sample solution based on those in the Resolution solution.

Calculate the percentage of each related fatty alcohol, alkane, or any unidentified impurity in the portion of Stearyl Alcohol taken:

Result = (r_U/r_T) × 100

r_U = peak response of each related fatty alcohol and alkane (or any unidentified impurity) from the Sample solution

r_T = sum of all the peak responses excluding peak responses due to solvent from the Sample solution

Acceptance criteria: Disregard peaks that are less than 0.05% for any unidentified impurities and any peaks due to solvent.

Branched primary and linear secondary fatty alcohols (2-hexyl-1-dodecanol, 2-octyl-1-decanol, 2-butyl-1-tetradecanol, 2-ethyl-1-hexadecanol, 4-octadecanol or 5-octadecanol, 3-octadecanol, nonadecanol, eicosanol): NMT 5.0%

Related linear fatty alcohols (lauryl alcohol, myristyl alcohol, cetyl alcohol, oleyl alcohol, linoleyl alcohol, arachidyl alcohol): NMT 1.0%

Related alkanes (octadecane, nonadecane, eicosane, heneicosane, docosane, branched docosanes): NMT 2.0%

Related unsaturated alcohols: NMT 1.0%

Sum of unidentified impurities: NMT 2.0%

Sum of related fatty alcohols, alkanes, and unidentified impurities: NMT 10.0%

5 SPECIFIC TESTS

Fats and Fixed Oils 〈401〉, Procedures, Acid Value: NMT 2

Fats and Fixed Oils 〈401〉, Procedures, Hydroxyl Value: 195–220

Fats and Fixed Oils 〈401〉, Procedures, Iodine Value: NMT 2

Water Determination 〈921〉, Method I, Method Ia: NMT 0.5%, using titrant: hydranal-composite 2 and solvent: hydranal-lipoSolver MH

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

Labeling: If a test for Impurities other than Organic Impurity Test 1 is used, the labeling states the test with which the article complies. Label it to indicate whether it is derived from vegetable, animal, or synthetic sources.

USP Reference Standards 〈11〉

USP Arachidyl Alcohol RS

USP Cetyl Alcohol RS

USP Lauryl Alcohol RS

USP Linolenyl Alcohol RS

USP Myristyl Alcohol RS

USP Oleyl Alcohol RS

USP Stearyl Alcohol RS