Zinc Acetate

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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C₄H₆O₄Zn · 2H₂O    219.50

C₄H₆O₄Zn 183.47

Acetic acid, zinc salt, dihydrate;

Zinc acetate dihydrate CAS RN®: 5970-45-6; UNII: FM5526K07A.

Zinc acetate anhydrous CAS RN®: 557-34-6; UNII: H2ZEY72PME.

1 DEFINITION

Zinc Acetate contains NLT 98.0% and NMT 102.0% of zinc acetate dihydrate (C₄H₆O₄Zn · 2H₂O). 

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, Acetate

Sample solution: 50 mg/mL

Acceptance criteria: Meets the requirements

3 ASSAY

Change to read:

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: 50 µg/mL of USP Zinc Acetate RS in Diluent prepared as follows. Transfer an appropriate portion of homogenized USP Zinc Acetate RS to a suitable volumetric ask. Add Diluent to about 50% of the nal ask volume to dissolve. Sonication may be needed to aid dissolution. Dilute with Diluent to volume.

Sample solution: 50 µg/mL of Zinc Acetate in Diluent, prepared as directed in the Standard solution

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, or 4.0-mm × 0.5-cm; 4.6-μm packing L91

Analytical: 4.0-mm × 25-cm; 9-µm packing L100, or 4.0-mm × 25-cm; 4.6-μm packing L91

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 acetate dihydrate (C₄H₆O₄Zn · 2H₂O) in the portion of Zinc Acetate 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 Acetate RS in the Standard solution (µg/mL)

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

Acceptance criteria: 98.0%–102.0%

4 IMPURITIES

4.1 Chloride and Sulfate 〈221〉, Chloride

Sample: 1.5 g

Acceptance criteria: The Sample shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.005%). • Chloride and Sulfate 〈221〉, Sulfate

Sample: 1.0 g

Acceptance criteria: The Sample shows no more sulfate than corresponds to 0.10 mL of 0.020 N sulfuric acid (0.010%). • Arsenic 〈211〉, Procedures, Procedure 1 and Procedure 2, Procedure 1: Colorimetry: NMT 3 ppm

Change to read:

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

Standard solution: 20 mL of 0.5 µg/mL of lead in 1% (v/v) nitric acid

Sample solution: Dissolve 0.5 g of Zinc Acetate in 1 mL of 50% (v/v) nitric acid in a separator. Add 3 mL of Ammonium citrate solution and 0.5 mL of Hydroxylamine hydrochloride solution, and render alkaline with ammonium hydroxide to phenol red TS. Add 10 mL of Potassium cyanide solution, and immediately extract the solution with successive 5-mL portions of Dithizone extraction solution, draining off each extract into another separator, until the last portion of the Dithizone extraction solution retains its green color. Shake the combined extracts for 30 s with 20 mL of 1% (v/v) nitric acid, and discard the chloroform layer.

Analysis: To the Standard solution and Sample solution, add 4 mL of Ammonium cyanide solution (IRA 1-Jun-2024) and 2 drops of Hydroxylamine hydrochloride solution. Add 10.0 mL of Standard dithizone solution, and shake the mixture for 30 s. Pass the chloroform layer through acid-washed filter paper into a color-comparison tube. Compare the color of the Sample solution with that of the Standard solution.

Acceptance criteria: The color of the Sample solution does not exceed the color of the Standard solution (0.002%).

4.2 Alkalies and Alkaline Earths

Sample solution: Dissolve 2.0 g in 150 mL of water in a 200-mL volumetric flask. Add sufficient ammonium sulfide TS to precipitate the zinc completely, and dilute with water to volume. Pass through a dry filter, rejecting the first portion of the filtrate.

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

Acceptance criteria: The weight of the residue does not exceed 2 mg (0.2%).

5 SPECIFIC TESTS

5.1 Insoluble Matter

Sample: 20 g

Analysis: Dissolve the Sample in 150 mL of water containing 1 mL of glacial acetic acid. Filter any undissolved residue, wash with water, and dry at 105°.

Acceptance criteria: NMT 1.0 mg of insoluble matter (0.005%)

5.2 pH 〈791〉

Sample solution: 50 mg/mL

Acceptance criteria: 6.0–8.0

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Zinc Acetate RS