Monosodium Glutamate

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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C₅H₈NNaO₄ . H₂O 187.13

l-Glutamic acid, sodium salt, hydrate;

Monosodium l-glutamate, hydrate    CAS RN®: 6106-04-3.

1 DEFINITION

Monosodium Glutamate contains NLT 99.0% and NMT 100.5% of monosodium glutamate (C₅H₈NNaO₄ . H₂O).

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A

B. Identification Tests-General 〈191〉, Sodium: It meets the requirements of test A.

3 ASSAY

3.1 Procedure

Sample: 250 mg

Titrimetric system

• (See Titrimetry 〈541〉.)
• Mode: Direct titration
• Titrant: 0.1 N perchloric acid VS
• Blank: 100 mL of glacial acetic acid with a few drops of water
• Endpoint detection: Potentiometric

Analysis: Wet the Sample with a few drops of water. Dissolve in 100 mL of glacial acetic acid. Titrate with 0.1 N perchloric acid VS. Perform a

blank determination.

Calculate the percentage of monosodium glutamate (C₅H₈NNaO₄ . H₂O) in the Sample taken:

Result = [(V_S − V_B) × N_A × F × 100]/W

V_S = Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL)

N_A = actual normality of the Titrant (mEq/mL)

F = equivalency factor, 93.56 mg/mEq

W = Sample weight (mg)

Acceptance criteria: 99.0%–100.5%

4 IMPURITIES

Chloride and Sulfate 〈221〉, Chloride: A 280-mg portion shows no more chloride than corresponds to 1.0 mL of 0.020 N hydrochloric acid (0.25%).

Change to read:

Lead 〈251〉, Procedures, Procedure 1: NMT 10 µg/g

5 SPECIFIC TESTS

5.1 Clarity and Color of Solution

Sample solution: 1.0 g in 10 mL of water

Standard solution: To 0.2 mL of a solution of sodium chloride containing 10 µg/mL of chloride ion (Cl), add 20 mL of water and mix. Then add 1 mL of 5 N nitric acid, 0.2 mL of dextrin solution (1 in 50), and 1 mL of silver nitrate TS, and allow to stand for 15 min.

Analysis: Compare the Sample solution with the Standard solution (see Visual Comparison 〈630〉).

Acceptance criteria: The Sample solution is colorless and has no more turbidity than the Standard solution.

5.2 Optical Rotation 〈781S〉, Procedures, Specific Rotation

Sample solution: 100 mg/mL in 2 N hydrochloric acid

Acceptance criteria: +24.8° to +25.3°, determined at 20°

5.3 pH 〈791〉: 6.7–7.2, in a solution (1 in 20)

5.4 Loss on Drying 〈731〉

Analysis: Dry at 100° for 5 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Monosodium Glutamate RS