Butylparaben

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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Portions of the monograph text that are national USP text, and are not part of the harmonized text, are marked with symbols (*) to specify this fact.

Benzoic acid, 4-hydroxy-, butyl ester;

Butyl p-hydroxybenzoate CAS RN: 94-26-8.

1 DEFINITION

Butylparaben contains NLT 98.0% and NMT 102.0% of C₁₁H₁₄O₃

2 IDENTIFICATION

Change to read:

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197M (CN 1-Mar-2020)

B. MELTING RANGE OR TEMPERATURE (741): 68°-71"

3 ASSAY

3.1 PROCEDURE

Mobile phase, Sample solution, Standard solution B, and Chromatographic system: Proceed as directed in the procedure for Related Substances.

System suitability

Sample: Standard solution B

Suitability requirements

Relative standard deviation: NMT 0.85% for six injections

Analysis

Samples: Sample solution and Standard solution B

Calculate the percentage of Butylparaben in the Sample solution:

Result=Px (r_U xC_S)/(r_SxC_U)

P = labeled purity of USP Butylparaben RS expressed as a percentage

r_U = peak area of butylparaben from the Sample solution

C_S = concentration of butylparaben in Standard solution B (mg/mL)

r_S = peak area of butylparaben from Standard solution B

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

Acceptance criteria: 98.0%-102.0%

4 IMPURITIES

RESIDUE ON IGNITION (281): NMT 0.1%, determined on a 1.0-g sample

RELATED SUBSTANCES

Mobile phase: Methanol and a 6.8 g/L solution of potassium dihydrogen phosphate (1:1 v/v)

Sample solution: Dissolve 50.0 mg of Butylparaben in 2.5 mL of methanol, and dilute with Mobile phase to 50.0 mL. Dilute 10.0 mL of this solution with Mobile phase to 100.0 mL.

Standard solution A: 5.0 µg/mL each of p-hydroxybenzoic acid, USP Propylparaben RS, and USP Butylparaben RS in Mobile phase

Standard solution B: Dissolve 50.0 mg of USP Butylparaben RS in 2.5 ml of methanol, and dilute with Mobile phase to 50.0 mL. Dilute 10.0 mL of this solution with Mobile phase to 100.0 mL.

Standard solution C: Dilute 1.0 mL of the Sample solution with Mobile phase to 20.0 mL. Dilute 1.0 mL of this solution with Mobile phase to 10.0 mL

Standard solution D: 50 µg/mL of iso-butylparaben in Mobile phase

Standard solution E: Standard solution D in Standard solution B (1 in 100)

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 272 nm

Column: 4.6-mm x 15-cm; 5-µm packing L1

Column temperature: 35°

Flow rate: 1.3 mL/min

Injection volume: 10 µL

Run time: About 1.5 times the retention time of butylparaben

4.1 System suitability

Sample: Standard solutions A and E

[NOTE-The retention time of butylparaben is about 22 min; the relative retention times for p-hydroxybenzoic acid, propylparaben, and iso-butylparaben with a reference to butylparaben are about 0.1, 0.5, and 0.9 min, respectively.]

Suitability requirements

Resolution: NLT 5.0 between the propylparaben and butylparaben peaks from Standard solution A and NLT 1.5 between the iso-butylparaben and butylparaben peaks from Standard solution E

4.2 Analysis

Samples: Sample solution and Standard solution C

[NOTE-Disregard any limit that is 0.2 times the area of the principal peak from Standard solution C (0.1%).]

Acceptance criteria

p-Hydroxybenzoic acid: The peak area from the Sample solution, multiplied by 1.4 to correct for the calculation of content, is NMT the area of the principal peak from Standard solution C (0.5%).

Unspecified impurities: The peak area of each impurity from the Sample solution is NMT the area of the principal peak from Standard solution C (0.5%).

Total impurities: The total peak area for all impurities from the Sample solution is NMT twice the area of the principal peak from Standard solution C (1.0%).

5 SPECIFIC TESTS

ACIDITY: To 2 mL of Butylparaben solution prepared in the Color of Solution test add 3 mL of alcohol, 5 mL of carbon dioxide-free water, and 0.1mL of bromocresol green TS. Titrate with 0.10 N sodium hydroxide.

Acceptance criteria: NMT 0.1 mL is required to produce a blue color.

6 COLOR OF SOLUTION

Butylparaben solution: Dissolve 1 g in alcohol, and dilute with alcohol to 10 mL..

Acceptance criteria: This solution is clear and not more intensely colored than alcohol or a solution prepared immediately before use by mixing 2.4 mL of ferric chloride CS, 1.0 mL of cobaltous chloride CS, and 0.4 mL of cupric sulfate CS with 0.3 N hydrochloric acid to make 10 ml, and diluting 5 mL of this solution with 0.3 N hydrochloric acid to make 100 mL. Make the comparison by viewing the solutions downward in matched color-comparison tubes against a white surface (see Color and Achromicity (631)).

7 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers.

USP REFERENCE STANDARDS (11)

USP Butylparaben RS

USP Propylparaben RS