Zinc Carbonate

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

3Zn(OH)₂ · 2ZnCO₃    548.96

Basic zinc carbonate;

Zinc subcarbonate CAS RN®: 5263-02-5; UNII: EQR32Y7H0M.

1 DEFINITION

Zinc Carbonate contains the equivalent of NLT 70.0% of Zinc oxide (ZnO).

2 IDENTIFICATION

A. Identification Tests—General 〈191〉, Chemical Identification Tests, Zinc

Sample solution: Dissolve in a slight excess of hydrochloric acid.

Acceptance criteria: Meets the requirements

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

3 ASSAY

Procedure

Diluent, Mobile phase, Post-column derivatization reagent, and System suitability: Prepare as directed in Zinc Determination 〈591〉, Procedure, Ion Chromatographic Method.

Standard stock solution: 2 mg/mL of USP Zinc Oxide RS, prepared as directed in Zinc Determination 〈591〉, Procedure, Ion Chromatographic Method

Standard solution: 20 µg/mL of USP Zinc Oxide RS in Diluent from the Standard stock solution

Sample solution: 27 µg/mL of Zinc Carbonate in Diluent prepared as follows. Transfer an appropriate portion of homogenized Zinc Carbonate 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.

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

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of zinc oxide (ZnO) in the portion of Zinc Carbonate 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 Oxide RS in the Standard solution (µg/mL)

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

Acceptance criteria: NLT 70.0%

4 IMPURITIES

4.1 Chloride and Sulfate 〈221〉, Chloride

Standard solution: 0.03 mL of 0.02 N hydrochloric acid

Sample solution: Dissolve 1.0 g of Zinc Carbonate in a mixture of 20 mL of water and 3 mL of nitric acid.

Acceptance criteria: The Sample solution shows no more chloride than the Standard solution (0.002%).

4.2 Sulfate

Standard solution: Dilute 0.10 mL of 0.02 N sulfuric acid with water to 10 mL.

Sample solution: Dissolve 10.0 g of Zinc Carbonate in a mixture of 75 mL of water and 10 mL of hydrochloric acid, and filter. Neutralize the filtrate with ammonium hydroxide, and dilute with water to 100 mL.

Analysis: To 10.0 mL each of the Standard solution and the Sample solution, add 1 mL of 0.6 N hydrochloric acid and 1 mL of barium chloride TS, and allow to stand for 10 min.

Acceptance criteria: The turbidity produced in the Sample solution is NMT that produced in the Standard solution (0.01%). Change to read:

4.3 Iron 〈241〉, Procedures, Procedure 1 (CN 1-Jun-2023)

Test preparation: Dissolve 0.5 g of Zinc Carbonate in 20 mL of water and 3 mL of hydrochloric acid.

Acceptance criteria: NMT 0.002%

4.4 Lead

Standard lead solution: Standard lead solution TS

Sample solution: Transfer 10.0 g of Zinc Carbonate to a 100-mL volumetric flask, add 20 mL of nitric acid and 10 mL of water, swirl to dissolve, and dilute with water to volume.

Blank: 4% (v/v) nitric acid in water

Instrumental conditions

(See Atomic Absorption Spectroscopy 〈852〉.)

Mode: Atomic absorption spectrophotometry

Analytical wavelength: 217.0 nm (lead emission line)

Lamp: Lead hollow-cathode

Flame: Air–acetylene

Analysis

Samples: Standard lead solution and Sample solution

Add 10.0 mL of the Sample solution to each of three 25-mL volumetric flasks. To the respective volumetric flasks add 0, 5.0, and 10.0 mL of Standard lead solution, and dilute with water to volume. These solutions contain 0, 0.002, and 0.004 mg/mL of added lead, respectively. Determine the absorbances of these three solutions. Plot the absorbances of the three solutions versus their contents of added lead, in mg/mL, as furnished by the Standard lead solution. Draw a straight line (calibration curve) best fitting the three points, and extrapolate the line until it intersects the concentration axis. From the intercept determine the concentration, in mg/mL, of lead in the Sample solution.

Calculate the quantity, in ppm, of lead in the portion of Zinc Carbonate taken:

Result = (V₁ /W) × (V₂ /V₃) × (C/F)

V₁ = total volume of the Sample solution, 100 mL

W = weight of Zinc Carbonate (g)

V₂ = nal volume of the solution used for analysis, 25 mL

V₃ = volume of the Sample solution used for analysis, 10 mL

C = concentration of lead in the Sample solution, as determined from the calibration curve (mg/mL)

F = conversion factor, 0.001 µg/mg

Acceptance criteria: NMT 5 ppm

4.5 Insoluble Matter

Sample: 10 g of Zinc Carbonate

Sample solution: Dissolve the Sample in a mixture of 100 mL of water and 7 mL of sulfuric acid.

Analysis: Heat the Sample solution on a steam bath for 1 h. Filter the solution through a tared sintered-glass crucible, wash with hot water, and dry the crucible at 105°. Cool, and weigh.

Acceptance criteria: The residue weighs NMT 2 mg (0.02%).

4.6 Substances Not Precipitated by Ammonium Sulfide

Sample: 1.0 g of Zinc Carbonate

Sample solution: Dissolve the Sample in 10 mL of water and 2 mL of sulfuric acid. Dilute with water to 80 mL, add 10 mL of ammonium hydroxide, and pass hydrogen sulfide through the solution for 30 min. Dilute with water to 100 mL, and allow the precipitate to settle. Decant the supernatant through a filter. Use the clear filtrate.

Analysis: Transfer 50 mL of the Sample solution to a tared dish, and evaporate to dryness. Ignite, gently at first, and nally at 800 ± 25°. Cool, and weigh.

Acceptance criteria: The weight of the residue is NMT 2 mg (0.4%).

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.