Zinc Chloride

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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ZnCl₂ 136.28

Zinc chloride CAS RN®: 7646-85-7; UNII: 86Q357L16B.

1 DEFINITION

Zinc Chloride contains NLT 97.0% and NMT 102.0% of zinc chloride (ZnCl₂).

2 IDENTIFICATION

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

B. Identification Tests—General 〈191〉, Chemical Identification Tests, Chloride: Meets the requirements

3 ASSAY

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Procedure

Diluent, Mobile phase, and (IRA 1-Jun-2024) Post-column derivatization reagent (IRA 1-Jun-2024) : Proceed as directed in Zinc

Determination 〈591〉, Procedure, Ion Chromatographic Method.

Standard solution: 30 µg/mL of USP Zinc Chloride RS in Diluent

Sample solution: 30 µg/mL of Zinc Chloride in Diluent

Chromatographic system: Proceed as directed in Zinc Determination 〈591〉, Procedure, Ion Chromatographic Method except for the Columns.

Columns

Guard: 4.0-mm × 5-cm; 9-µm packing L100. [Note—Alternatively, a 4.0-mm × 0.5-cm; 4.6-µm packing L91 column may be used.] Analytical: 4.0-mm × 25-cm; 9-µm packing L100. [Note—Alternatively, a 4.0-mm × 25-cm; 4.6-µm packing L91 column may be used.]

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 0.73% (IRA 1-Jun-2024)

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of zinc chloride (ZnCl₂ ) in the portion of Zinc Chloride taken:

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

r_U = peak response of zinc from the Sample solution

r_S = peak response of zinc from the Standard solution

C_S = concentration of USP Zinc Chloride RS in the Standard solution (µg/mL)

C_U = concentration of Zinc Chloride in the Sample solution (µg/mL)

Acceptance criteria: 97.0%–102.0%

4 IMPURITIES

4.1 Chloride and Sulfate 〈221〉, Sulfate

Standard solution: 0.20 mL of 0.020 N sulfuric acid

Sample solution: 1.0 g of Zinc Chloride in 30 mL of water

Acceptance criteria: 20 mL of the Sample solution shows no more sulfate than the Standard solution (0.03%).

4.2 Lead 〈251〉, Procedures, Procedure 1: Chemical Method

Potassium cyanide solution: Prepare as directed in 〈251〉.

Standard solution: Add 5 mL of water, 2.50 mL of standard lead solution TS, and 15 mL of Potassium cyanide solution (100 mg/mL) to a color-comparison tube.

Sample solution: Dissolve 0.50 g of Zinc Chloride in 5 mL of water, and transfer the solution to a similar color-comparison tube. Add 15 mL of Potassium cyanide solution (100 mg/mL), and allow the mixture to become clear.

Analysis: To each tube add 0.1 mL of sodium sulde TS. Mix the contents of each tube, and allow to stand for 5 min.

Acceptance criteria: Viewed downward over a white surface, the Sample solution is not darker than the Standard solution (NMT 0.005%).

4.3 Limit of Ammonium Salts

Sample solution: 100 mg/mL of Zinc Chloride in water

Analysis: To 5 mL of the Sample solution add 1 N sodium hydroxide until the precipitate rst formed is redissolved, then warm the solution.

Acceptance criteria: No odor of ammonia is perceptible.

4.4 Limit of Oxychloride

Sample solution: Dissolve 1.0 g of Zinc Chloride in 20 mL of water, and add 20 mL of alcohol.

Analysis: To 10 mL of the Sample solution add 0.30 mL of 1.0 N hydrochloric acid.

Acceptance criteria: The solution becomes perfectly clear.

4.5 Alkalies and Alkaline Earths

Sample solution: Dissolve 2.0 g of Zinc Chloride in 150 mL of water contained in a 200-mL volumetric flask. Add sucient ammonium sulde TS to precipitate the zinc completely, and dilute with water to volume. Pass through a dry lter, and discard the rst portion of the ltrate.

Analysis: To 100 mL of the Sample solution add 5 drops of sulfuric acid. Evaporate to dryness, and ignite.

Acceptance criteria: The weight of the residue is NMT 10 mg (1.0%).

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Zinc Chloride RS