Sodium Benzoate

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

Sodium Benzoate contains NLT 99.0% and NMT 101.0% of sodium benzoate (C₇H₅NaO₂), calculated on the anhydrous basis.

2 IDENTIFICATION

Change to read:

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

Sample: Undried sample

Acceptance criteria: Meets the requirements

B. IDENTIFICATION TESTS—GENERAL, Sodium 〈191〉: Meets the requirements

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

3 ASSAY

3.1 PROCEDURE

Solution A: Adjust a 20-mM solution of monobasic potassium phosphate with phosphoric acid to a pH of 2.5.

Mobile phase: Solution A and acetonitrile (70:30)

Diluent: Water and acetonitrile (50:50)

System suitability solution: 0.1 mg/mL of USP Salicylic Acid RS and 0.1 mg/mL of USP Benzoic Acid RS in Diluent Standard solution: 0.1 mg/mL of USP Benzoic Acid RS in Diluent

Sample solution: 0.1 mg/mL of Sodium Benzoate in Diluent

3.1.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 230 nm

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

Column temperature: 25°

Flow rate: 1.0 mL/min Injection volume: 10 µL

3.1.2 System suitability

Samples: System suitability solution and Standard solution

[NOTE—The relative retention times for benzoic acid and salicylic acid are approximately 1.0 and 1.2, respectively.]

Suitability requirements

Resolution: NLT 3.0 between benzoic acid and salicylic acid, System suitability solution Relative standard deviation: NMT 0.5% for benzoic acid, Standard solution

Tailing factor: NMT 2.0 for benzoic acid, Standard solution

3.1.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of sodium benzoate (C H NaO ) in the portion of Sodium Benzoate taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 100

r_U = peak area of benzoic acid from the Sample solution

r_S = peak area of benzoic acid from the Standard solution

C_S = concentration of benzoic acid in the Standard solution, corrected for purity (mg/mL)

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

M_r1 = molecular weight of sodium benzoate, 144.10

M_r2 = molecular weight of benzoic acid, 122.12

Acceptance criteria: 99.0%–101.0% on the anhydrous basis SPECIFIC TESTS

3.2 WATER DETERMINATION

Method I 〈921〉: NMT 1.5%

3.3 ALKALINITY

Sample solution: 2 g in 20 mL of hot water

Analysis: To the Sample solution add 2 drops of phenolphthalein TS.

Acceptance criteria: The pink color produced, if any, is discharged by the addition of 0.20 mL of 0.10 N sulfuric acid.

4 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers.

USP REFERENCE STANDARDS 〈11〉

USP Benzoic Acid RS USP Salicylic Acid RS USP Sodium Benzoate RS