Aminobenzoic Acid Gel

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

Aminobenzoic Acid Gel contains NLT 90.0% and NMT 110.0% of the labeled amount of aminobenzoic acid (C₇H₇NO₂).

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K _{(CN 1-May-2020)}

Change to read:

B. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U _{(CN 1-May-2020)}

Sample solution: 5 µg/mL in alcohol

Acceptance criteria: Meets the requirements

3 ASSAY

Procedure

Mobile phase: Methanol, glacial acetic acid, and water (30:1:69). Allow the mixture to cool, and pass, if necessary, through a suitable microporous membrane filter, and degas.

Internal standard solution: 7 mg/mL of salicylic acid in methanol; dissolve by sonicating.

Standard stock solution: 0.42 mg/mL of USP Aminobenzoic Acid RS in methanol; dissolve by sonicating.

Standard solution: 0.042 mg/mL of USP Aminobenzoic Acid RS in methanol prepared as follows. Transfer 5 mL each of Standard stock solution and Internal standard solution into a 50-mL volumetric ask, and dilute with methanol to volume. Pass through 0.6-µm filter paper. Throughout the preparation, protect against actinic light.

Sample solution: Nominally 0.042 mg/mL of aminobenzoic acid in methanol prepared as follows. Transfer a quantity of Gel, equivalent to 4.2 mg of aminobenzoic acid, into a 100-mL volumetric ask. Add 10.0 mL of Internal standard solution and 50 mL of methanol. Shake or sonicate, as necessary, and dilute with methanol to volume. Filter, if necessary, through filter paper (Whatman No. 41 or equivalent). Pass through 0.6-µm filter paper. Throughout this preparation, protect against actinic light.

3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 3.9-mm × 30-cm; packing L11

Flow rate: 1.0 mL/min

Injection volume: 15 µL

System suitability

Sample: Standard solution

Chromatograph replicate 15-µL injections of the Standard solution until the response ratio variability is within 1.0% of average.

[Note—The relative retention times for aminobenzoic acid and salicylic acid are about 1.0 and 3.0, respectively.]

3.2 Suitability requirements

Resolution: NLT 3.0 between aminobenzoic acid and salicylic acid peaks

3.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of aminobenzoic acid (C₇H₇NO₂) in the portion of Gel taken:

Result = (R_U /R_S ) × (C_S /C_U ) × 100

R_U = peak response ratio of aminobenzoic to salicylic acid from the Sample solution

R_S = peak response ratio of aminobenzoic to salicylic acid from the Standard solution

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

C_U = nominal concentration of aminobenzoic acid in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–110.0%

4 OTHER COMPONENTS

Alcohol Determination, Method II〈611〉: 42.3%–54.0% (w/w) of C₂H₅OH

5 PERFORMANCE TESTS

Minimum Fill 〈755〉: Meets the requirements

6 SPECIFIC TESTS

pH 〈791〉: 4.0–6.0

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers.

USP Reference Standards 〈11〉

USP Aminobenzoic Acid RS.