Cetostearyl 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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Mixture of cetyl and stearyl alcohols (NF 1-Dec-2023)

CAS RN®: 67762-27-0.

1 DEFINITION

Cetostearyl Alcohol contains NLT 40.0% of stearyl alcohol (C₁₈H₃₈O), and the sum of the stearyl alcohol content and the Cetyl alcohol (C₁₆H₃₄O) content is NLT 90.0% and NMT 102.0%. It is obtained from sources of vegetable, animal, or synthetic origin.

2 IDENTIFICATION

 A. Chromatographic Identity

Analysis: Proceed as directed in the Assay.

Acceptance criteria: The retention times of the major peaks of the Sample solution, excluding the solvent and internal standard peaks, correspond to the cetyl alcohol and stearyl alcohol peaks of the System suitability solution.

3 ASSAY

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 the 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: To match the cetyl alcohol and stearyl alcohol ratio in the test sample, prepare the sum of 2.0 mg/mL of USP Cetyl Alcohol 

RS and USP Stearyl Alcohol RS in the Internal standard solution. Heat the solution in a sealed container in a 50° water bath until cetyl alcohol and stearyl alcohol are dissolved. Allow the solution to cool to room temperature, and mix well.

Sample solution: Prepare 2.0 mg/mL of Cetostearyl Alcohol in the Internal standard solution, and heat the solution in a sealed container in a 50° water bath until the cetostearyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

3.2 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

3.3 System suitability

Samples:

System suitability solution and Standard solution

[Note-See Table 2 for the relative retention times.]

Table 2

3.4 Suitability requirements

Resolution: NLT 30 between the cetyl alcohol and stearyl alcohol peaks; NLT 2.0 between the stearyl alcohol and oleyl alcohol peaks,

3.5 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

3.6 Analysis

Samples: Standard solution and Sample solution

Calculate the percentages of cetyl alcohol (C₁₆H₃₄O) or stearyl alcohol (C₁₈H₃₈O) in the portion of Cetostearyl Alcohol taken:

Result = (R_U/R_S) × (C_S/C_U) × 100

R_^U = peak response ratio of cetyl alcohol (or stearyl alcohol) to the internal standard from the Sample solution

R_S = peak response ratio of cetyl alcohol (or stearyl alcohol) to the internal standard from the Standard solution

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

C_U = concentration of Cetostearyl Alcohol in the Sample solution (mg/mL)

3.7 Acceptance criteria

Stearyl alcohol (C₁₈H₃₈O): NLT 40.0%

Sum of stearyl alcohol (C₁₈H₃₈O) and cetyl alcohol (C₁₆H₃₄O): 90.0%–102.0%

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%, determined on 2 g

Change to read:

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 Linoleyl Alcohol RS, (NF 1-Dec-2023) 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 Linoleyl Alcohol RS, (NF 1-Dec-2023) USP Linolenyl Alcohol RS, and USP Arachidyl Alcohol RS.

Sample solution: 1 mg/mL of Cetostearyl Alcohol in ethanol. Heat the solution in a sealed container in a 50° water bath until the cetostearyl 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 Injection type.

Injection type: Split; split ratio 5:1

System suitability

Sample: Resolution solution

[Note-The relative retention times in Table 3 are provided as information that could aid in peak assignment. (NF 1-Dec-2023) ]

Table 3

Suitability requirement

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 alcohol and oleyl alcohol peaks

Analysis

Samples: Resolution solution and Sample solution Identify each related fatty alcohol peak in the Sample solution based on that in the Resolution solution.

Calculate the percentage of each related fatty alcohol or any unidentified (NF 1-Dec-2023) impurity in the portion of Cetostearyl Alcohol taken:

Result = (r_U /r_T ) × 100

r_U = peak response of each related fatty alcohol (or any unidentified (NF 1-Dec-2023) 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 (NF 1-Dec-2023) impurities, and any peaks due to solvent.

Sum of unidentified (NF 1-Dec-2023) impurities: NMT 1%

Related unsaturated fatty alcohols: NMT 4% (NF 1-Dec-2023)

Sum of related fatty alcohols and unidentified (NF 1-Dec-2023) impurities: NMT 10.0%

5 SPECIFIC TESTS

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

Fats and Fixed Oils 〈401〉, Hydroxyl Value: 208–228

Delete the following:

Fats and Fixed Oils 〈401〉, Iodine Value (NF 1-Dec-2023)

Water Determination 〈921〉, Method I: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

Labeling: Label it to indicate whether it is derived from vegetable, animal, or synthetic sources.