Butyl Palmitostearate

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

Butyl Palmitostearate is a mixture of the butyl ester of stearic acid (C₁₆H₃₂O₂) and the butyl ester of palmitic acid (C₁₈H₃₆O₂). It contains 40.0%– 80.0% of butyl stearate (C₂₂H₄₄O₂). The total percentage of butyl stearate (C₂₂H₄₄O₂) and butyl palmitate (C₂₀H₄₀O₂) is NLT 90.0%. 

2 IDENTIFICATION

A. It meets the requirements of the test for Content of Butyl Palmitate and Butyl Stearate.

3 ASSAY

Content of Butyl Palmitate and Butyl Stearate

Standard solution A: 2.0 mg/mL of USP Butyl Stearate RS in chloroform

Standard solution B: 1.0 mg/mL of USP Butyl Palmitate RS in chloroform

System suitability solution: 1.4 µg/mL of USP Butyl Stearate RS and 1.0 µg/mL of USP Butyl Palmitate RS in chloroform, prepared from Standard solution A, Standard solution B, and chloroform

Sample solution: 2.0 mg/mL of Butyl Palmitostearate in chloroform

4 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm × 30-m capillary; bonded with a 0.25-µm layer of thickness of phase G27

Temperatures

Detector: 280°

Injection port: 280°

Column: See Table 1.

Table 1

Carrier gas: Helium

Flow rate: 1.4 mL/min

Injection volume: 1 µL

Injection type: Split injection, split ratio is 5:1

4.1 System suitability

Samples: Standard solution A and System suitability solution

[Note—The relative retention times for butyl palmitate and butyl stearate are 0.91 and 1.00, respectively.]

System suitability requirements

Resolution: NLT 20 between butyl palmitate and butyl stearate, System suitability solution

Tailing factor: NMT 2.0 for the butyl stearate peak, System suitability solution

Relative standard deviation: NMT 3.0% for the butyl stearate peak, Standard solution A

4.2 Analysis

Samples: Standard solution A, Standard solution B, and Sample solution

Identify the butyl palmitate and butyl stearate peaks in the Sample solution based on those in Standard solution A and Standard solution B. Calculate the percentage of butyl palmitate or butyl stearate in the portion of Butyl Palmitostearate taken:

Result = (r_U /r_S ) × (C_S /C_U ) × 100

r_U = peak response of butyl palmitate or butyl stearate from the Sample solution

r_S = peak response of butyl palmitate from Standard solution B or peak response of butyl stearate from Standard solution A

C_S = concentration of USP Butyl Palmitate RS in Standard solution B or concentration of USP Butyl Stearate RS in Standard solution A

C_U = concentration of Butyl Palmitostearate in the Sample solution 

4.3 Acceptance criteria

Content of butyl stearate: 40.0%–80.0%

Sum of butyl stearate and butyl palmitate: NLT 90.0%

5 SPECIFIC TESTS

Melting Range or Temperature, Class II〈741〉: 17°–24°

Fats and Fixed Oils, Acid Value〈401〉: NMT 0.5

Fats and Fixed Oils, Iodine Value〈401〉: NMT 1.0

Fats and Fixed Oils, Saponification Value〈401〉: 165–180

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

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers. Store at room temperature. Keep away from heat and sources of ignition.

USP Reference Standards 〈11〉

USP Butyl Palmitate RS

USP Butyl Stearate RS