Lysine Hydrochloride

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

Lysine Hydrochloride contains NLT 98.5% and NMT 101.5% of l-lysine hydrochloride (C₆H₁₄N₂O₂ · HCl), calculated on the dried basis.

2 IDENTIFICATION

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

3 ASSAY

Procedure

Sample: 90 mg of Lysine Hydrochloride

Blank: Mix 3 mL of formic acid and 50 mL of glacial acetic acid.

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.1 N perchloric acid VS

Endpoint detection: Potentiometric

Analysis: Dissolve the Sample in 3 mL of formic acid and 50 mL of glacial acetic acid. Add 10 mL of mercuric acetate TS, and titrate with theTitrant. Perform the Blank determination.

Calculate the percentage of lysine hydrochloride (C₆H₁₄N₂O₂ · HCll) in the Sample taken:

Result = {[(V_S − V_B) × N × F]/W} × 100

V_S = Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL)

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

F = equivalency factor, 91.33 mg/mEq

W = Sample weight (mg)

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

4 OTHER COMPONENTS

Content of Chloride

Sample: 350 mg of Lysine Hydrochloride

Blank: 140 mL of water

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.1 N silver nitrate VS

Endpoint detection: Visual

Analysis: Transfer the Sample to a porcelain casserole, and add 140 mL of water and 1 mL of dichlorofluorescein TS. Titrate with the Titrant until the silver chloride occulates and the mixture acquires a faint pink color. Perform the Blank determination.

Calculate the percentage of chloride (Cl) in the Sample taken:

Result = {[(V_S − V_B) × N × F]/W} × 100

V_S = Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL)

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

F = equivalency factor, 35.45 mg/mEq

W = Sample weight (mg)

Acceptance criteria: 19.0%–19.6%

5 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Chloride and Sulfate, Sulfate〈221〉

Standard solution: 0.10 mL of 0.020 N sulfuric acid

Sample: 0.33 g of Lysine Hydrochloride

Acceptance criteria: NMT 0.03%

Change to read:

Iron 〈241〉, Procedures, Procedure 1 (CN 1-Jun-2023) : NMT 30 ppm

Change to read:

Related Compounds

Standard solution: 0.05 mg/mL of USP l-Lysine Hydrochloride RS in water. [Note—This solution has a concentration equivalent to 0.5% of that of the Sample solution.]

Sample solution: 10 mg/mL of Lysine Hydrochloride in water

System suitability solution: 0.4 mg/mL each of USP l-Lysine Hydrochloride RS and USP Arginine Hydrochloride RS

Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Mode: TLC

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture

Application volume: 5 μL

Developing solvent system: Isopropyl alcohol and ammonium hydroxide (7:3)

Spray reagent: 2 mg/mL (ERR 1-Jun-2023) of ninhydrin in a mixture of butyl alcohol and 2 N acetic acid (95:5)

System suitability

Suitability requirements: The chromatogram of the System suitability solution exhibits two clearly separated spots.

Analysis

Samples: Standard solution, System suitability solution, and Sample solution

Dry the plate between 100° and 105° until the ammonia completely disappears. Spray with Spray reagent, and heat between 100° and 105° for 15 min. Examine the plate under white light.

Acceptance criteria: Any secondary spot of the Sample solution is not larger or more intense than the principal spot of the Standard solution.

Individual impurities: NMT 0.5%

Total impurities: NMT 2.0%

6 SPECIFIC TESTS

Optical Rotation, Specific Rotation〈781S〉

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

Acceptance criteria: +20.4° to +21.4°

Loss on Drying 〈731〉: Dry a sample at 105° for 3 h: it loses NMT 0.4% of its weight.

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Arginine Hydrochloride RS

USP l-Lysine Hydrochloride RS