Cetyl 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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1 DEFINITION

Cetyl alcohol contains NLT 90.0% and NMT 102.0% of cetyl alcohol (C₁₆H₃₄O), 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 cetyl alcohol peak 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 Internal standard solution, and 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 Cetyl Alcohol RS in Internal standard solution, and heat the solution in a sealed container in a 50° water bath until cetyl alcohol is dissolved. Allow the solution to cool to room temperature, and mix well.

Sample solution: Prepare 1.0 mg/mL of Cetyl Alcohol in Internal standard solution, and heat the solution in a sealed container in a 50° water bath until cetyl 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 x 30-m fused-silica capillary; coated with a 0.25-µm layer of phase G7

Temperatures

Injection port: 270°

Detector: 280°

Column: See Table 1.

Table 1

Carrier gas: Hydrogen

Flow rate: 2mL/min constant flow mode

Injection volume: 1µL

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.]

USP-NF Cetyl Alcohol

Table 2

Suitability requirements

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

Tailing factor: 0.8-1.8 for the cetyl alcohol and 1-pentadecanol peaks, Standard solution

Relative standard deviation: NMT 1%, using the area ratio of cetyl alcohol to 1-pentadecanol, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of cetyl alcohol (C₁₆H₃₄O) in the portion of Cetyl Alcohol taken:

Result = (R_U/R_S) × (C_S/C_U) × 100

R_U = peak response ratio of cetyl alcohol to the internal standard from the Sample solution

R_S = peak response ratio of cetyl alcohol to the internal standard from the Standard solution

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

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

Acceptance criteria: 90.0%-102.0%

4 IMPURITIES

RESIDUE ON IGNITION (281): NMT 0.1%, determined on 2 g

Change to read:

[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). (IRA 1-Nov-2020)

Change to read:

ORGANIC IMPURITY TEST 1: (IRA 1-Nov-2020) LIMIT OF RELATED FATTY ALCOHOLS

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

Resolution solution: Prepare 1 mg/mL of USP Lauryl Alcohol RS, 1 mg/mL of USP Myristyl Alcohol RS, 1 mg/mL of USP Cetyl Alcohol RS, 1 mg/mL of USP Stearyl Alcohol RS, and 1 mg/mL of USP Oleyl 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 have 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, and USP Oleyl Alcohol RS.

Sample solution: Prepare 1.0 mg/mL of Cetyl Alcohol in ethanol, and heat the solution in a sealed container in a 50° water bath until cetyl 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 alcohol 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 (IRA 1-Nov-2020) impurity in the portion of Cetyl Alcohol taken:

Result = (r_U/r_T) x 100

r_U = peak response of each related fatty alcohol (or any unidentified (IRA 1-Nov-2020) 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 (IRA 1-Nov-2020) impurities and any peaks due to solvent.

Sum of unidentified (IRA 1-Nov-2020) impurities: NMT 1%

Sum of related fatty alcohols and unidentified (IRA 1-Nov-2020) impurities: NMT 10.0%

Add the following:

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, and USP Oleyl 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 have 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, and USP Oleyl Alcohol RS.

Sample solution: Prepare 1.0 mg/mL of Cetyl Alcohol in ethanol, and heat the solution in a sealed container in a 50° water bath until cetyl 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 Linear secondary fatty alcohols.

d Related branched-chain fatty alcohol.

e Internal standard.

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 alcohol 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, unsaturated alcohol, or any other unidentified related fatty alcohol or impurity in the portion of Cetyl Alcohol taken:

Result = (r_U/r_T) x 100

r_U = peak response of each related fatty alcohol, alkane, and unsaturated 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.

Branched primary and linear secondary fatty alcohols (2-hexyl-1-decanol, 2-butyl-1-dodecanol, 2-ethyl-1-tetradecanol, 3-hexadecanol,

4-hexadecanol or 5-hexadecanol, heptadecanol, 2-heptadecanol, octadecanol): NMT 5.0%

Related linear fatty alcohols (lauryl alcohol, myristyl alcohol, stearyl alcohol, oleyl alcohol): NMT 1.0%

Related alkanes (octadecane, nonadecane, eicosane, branched eicosanes): NMT 1.0%

Related unsaturated alcohols: NMT 1.0%

Sum of unidentified impurities: NMT 1.5%

Sum of related fatty alcohols, alkanes, and unidentified impurities: NMT 10.0% (IRA 1-Nov-2020)

5 SPECIFIC TESTS

FATS AND FIXED OILS (401), Procedures, Acid Value: NMT 2

FATS AND FIXED OILS (401), Procedures, Hydroxyl Value: 218-238

FATS AND FIXED OILS (401), Procedures, lodine Value: NMT 5

Change to read:

WATER DETERMINATION (921), Method J, Method la: (IRA 1-Nov-2020) NMT 0.5%

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers.

Change to read:

LABELING : If a test for Impurities other than Organic Impurity Test 1 is used, the labeling states the test with which the article complies. (IRA 1-Nov-2020) Label it to indicate whether it is derived from vegetable, animal, or synthetic sources.

USP REFERENCE STANDARDS (11).

USP Cetyl Alcohol RS

USP Lauryl Alcohol RS

USP Myristyl Alcohol RS

USP Oleyl Alcohol RS

USP Stearyl Alcohol RS