Aspartic Acid

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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C₄H₇NO₄  133.10

L-Aspartic acid CAS RN^®: 56-84-8; UNII: 30KYC7MIAI.

1 DEFINITION

Aspartic Acid contains NLT 98.5% and NMT 101.5% of aspartic acid (C₄H₇NO₄), calculated on the dried basis.

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197K

3 ASSAY

3.1 PROCEDURE

Sample: 100 mg of Aspartic Acid

Titrimetric system

(See Titrimetry (541).)

Mode: Direct titration

Titrant: 0.1 N sodium hydroxide VS

Endpoint detection: Visual

Blank: 50 mL of carbon dioxide-free water. Add 0.1 mL of bromothymol blue TS.

Analysis: Transfer the Sample to a 125-mL flask, and dissolve in 50 mL of carbon dioxide-free water. Heat slightly if necessary. Cool, add 0.1 mL of bromothymol blue TS, and titrate with Titrant until the color changes from yellow to blue. Perform the blank determination.

Calculate the percentage of aspartic acid (C₄H₇NO₄) in the portion of Aspartic Acid taken:

Result = [(V_S - V_B x N_A x F x 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, 133.1 mg/mEq

W = Sample weight (mg)

Acceptance criteria: 98.5%-101.5% on the dried basis

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281)

NMT 0.1%

4.2 CHLORIDE AND SULFATE (221), Chloride

Sample solution: Dissolve 0.7 g of Aspartic Acid in 10 mL of diluted nitric acid, and dilute with water to 15 mL.

Acceptance criteria: The Sample solution shows no more chloride than corresponds to 0.20 mL of 0.020 N hydrochloric acid (NMT 0.02%).

4.3 CHLORIDE AND SULFATE (221), Sulfate

Sample solution: Dissolve 0.8 g of Aspartic Acid in 4 mL of hydrochloric acid, and dilute with water to 15 mL.

Acceptance criteria: The Sample solution shows no more sulfate than corresponds to 0.25 mL of 0.020 N sulfuric acid (NMT 0.03%).

Change to read:

4.4 IRON (241), Procedures, Procedure 1 (CN 1-JUN-2023)

NMT 10 ppm

4.5 RELATED COMPOUNDS

Mobile phase: 0.008 N sulfuric acid

System suitability solution: A mixture of 0.1 mg/mL of USP Fumaric Acid RS, 0.05 mg/mL of USP Maleic Acid RS, and 1.5 mg/mL of USP

Malic Acid RS in water

Fumaric acid standard solution: 0.1 mg/mL of USP Fumaric Acid RS in water

Maleic acid standard solution: 0.05 mg/mL of USP Maleic Acid RS in water

Malic acid standard solution: 1.5 mg/mL of USP Malic Acid RS in water

Sample solution: Transfer 10 g of Aspartic Acid to a 100-mL volumetric flask, add 15-20 mL of 6 N hydrochloric acid, and mix to dissolve.

Dilute with water to volume.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 214 nm

Column: 7.8-mm x 30-cm; 9-µm packing L17

Column temperature: 30°

Flow rate: 0.6 mL/min

Injection volume: 10 µL

System suitability

Sample: System suitability solution

[NOTE-See Table 1 for the relative retention times.]

Suitability requirements

Resolution: NLT 1.5 between maleic acid and malic acid

Relative standard deviation: NMT 10.0% each for maleic acid, malic acid, and fumaric acid

Analysis

Samples: Standard solutions and Sample solution

[NOTE-A hydrochloric acid peak at around 6-7 min may be observed in the chromatogram of the Sample solution. Disregard this peak in the calculation of the impurity.]

Calculate the percentage of each specified acid in the portion of Aspartic Acid taken:

Result = (r_U/r_S) x (C_S/C_U) × 100

r_U = peak response of any unspecified impurity from the Sample solution

r_S = peak response of fumaric acid from the Fumaric acid standard solution 

C_S = concentration of USP Fumaric Acid RS in the Fumaric acid standard solution (mg/mL)

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

Acceptance criteria: See Table 1.

Table 1

5 SPECIFIC TESTS

5.1 OPTICAL ROTATION (781S), Procedures, Specific Rotation

Sample solution: 80 mg/mL in 6 N hydrochloric acid

Acceptance criteria: +24.0° to +26.0°, at 20°

5.2 LOSS ON DRYING (731)

Analysis: Dry at 105° for 3 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in well-closed containers, and store protected from light.

6.2 USP REFERENCE STANDARDS (11)

USP Aspartic Acid RS

USP Fumaric Acid RS

USP Maleic Acid RS

USP Malic Acid RS