Octinoxate

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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C₁₈H₂₆O₃  290.40

2-Propenoic acid, 3-(4-methoxyphenyl)-, 2-ethylhexyl ester;

2-Ethylhexyl p-methoxycinnamate

CAS RN^®: 5466-77-3; UNII: 4Y5P7MUD51

1 DEFINITION

Octinoxate contains NLT 95.0% and NMT 105.0% of octinoxate (C₁₈H₂₆O₃), calculated on the as-is basis.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or 197F (CN 1-May-2020)

B. The retention time of the octinoxate peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 Procedure

System suitability stock solution: 5% (v/v) USP Benzyl Benzoate RS in acetone

System suitability solution: 50 mg/mL of USP Octinoxate RS in System suitability stock solution

Standard solution: 50 mg/mL of USP Octinoxate RS in acetone

Sample solution: Transfer 5 mL of Octinoxate to a 100-mL volumetric flask, and dilute with acetone to volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm × 25-m; 0.25-µm thickness of phase G1

Carrier gas: Helium

Temperatures

Injection port: 250°

Detector: 300°

Column: See Table 1.

Table 1

Flow rate: 2 mL/min

Injection volume: 1 µL

Injection type: Split ratio, 85:1

System suitability

Samples: System suitability solution and Standard solution

[Note—The relative retention times for benzyl benzoate and octinoxate are about 0.68 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 20 between benzyl benzoate and octinoxate, System suitability solution

Relative standard deviation: NMT 2.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of octinoxate (C₁₈H₂₆O₃) in the portion of Octinoxate taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of octinoxate from the Sample solution

r_S = peak response of octinoxate from the Standard solution

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

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

Acceptance criteria: 95.0%–105.0% on the as-is basis

4 IMPURITIES

4.1 Organic Impurities

System suitability stock solution, System suitability solution, Standard solution, Chromatographic system, and System suitability: Proceed as directed in the Assay.

Sample solution: Transfer 5 mL of Octinoxate to a 100-mL volumetric flask, and dilute with acetone to volume.

Analysis

Sample: Sample solution

Calculate the percentage of each impurity in the portion of Octinoxate taken:

Result = (r_U/r_T) × 100

r_U = peak response of each impurity from the Sample solution

r_T = sum of all the peak responses from the Sample solution

Acceptance criteria

Any individual impurity: NMT 0.5%

Total impurities: NMT 2.0%

5 SPECIFIC TESTS

Specific Gravity 〈841〉: 1.005–1.013

Refractive Index 〈831〉: 1.542–1.548 at 20°

Acidity

Sample: 5 mL of Octinoxate

Analysis: Add 50 mL of alcohol to the Sample, and mix. Add 4 drops of phenolphthalein TS, and titrate with 0.1 N sodium hydroxide.

Acceptance criteria: NMT 0.8 mL of 0.1 N sodium hydroxide is required.

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers, and store in a cool place.

USP Reference Standards 〈11〉

USP Benzyl Benzoate RS

Benzoic acid, phenylmethyl ester.

C₁₄H₁₂O₂ 212.24

USP Octinoxate RS