Butyl Stearate

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 Stearate consists of the esters of butyl alcohol and fatty acids composed chiefly of stearic acid (C₁₈H₃₆O₂) and a minor amount of palmitic acid (C₁₆H₃₂O₂). It contains NLT 90.0% of butyl stearate [C₂₂H₄₄O₂(M_w340.59)], and the total of butyl stearate (C₂₂H₄₄O₂) and butyl palmitate [C₂₀H₄₀O₂(M_w312.53)] is NLT 96.0%.

2 IDENTIFICATION

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

3 ASSAY

3.1 CONTENT OF BUTYL PALMITATE AND BUTYL STEARATE

Standard solution A: 2.0 mg/mL of USP Butyl Stearate RS in chloroform Standard solution B: 0.2 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 Stearate in chloroform

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.

3.2 System suitability

Samples: System suitability solution and Standard solution A

[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

3.3 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 Stearate 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 Stearate in the Sample solution

Acceptance criteria: NLT 90.0% of butyl stearate and NLT 96.0% for the sum of butyl stearate and butyl palmitate

4 SPECIFIC TESTS

MELTING RANGE OR TEMPERATURE, Class II〈741〉: 19°–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%

5 ADDITIONAL REQUIREMENTS

5.1 PACKAGING AND STORAGE

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

5.2 USP REFERENCE STANDARDS 〈11〉

USP Butyl Palmitate RS

USP Butyl Stearate RS