Zinc Gluconate Tablets

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

1 DEFINITION

Zinc Gluconate Tablets contain NLT 93.0% and NMT 107.0% of the labeled amount of Zn, in the form of zinc gluconate (C₁₂H₂₂O₁₄Zn). 

2 IDENTIFICATION

2.1 A. Thin-Layer Chromatography

Standard solution: USP Potassium Gluconate RS in water; 10 mg/mL

Sample solution: Transfer a weighed quantity of powdered Tablets to a suitable flask, and add the necessary volume of water to obtain a solution containing about 10 mg/mL of zinc gluconate. Shake and sonicate, heating in a water bath at 60°, if necessary, and filter.

2.1.1 Chromatographic system

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

Mode: TLC

Adsorbent: 0.25-mm layer of chromatographic silica gel

Application volume: 5 µL

Developing solvent system: Alcohol, water, ammonium hydroxide, and ethyl acetate (50:30:10:10)

Spray reagent: Dissolve 2.5 g of ammonium molybdate in about 50 mL of 2 N sulfuric acid in a 100-mL volumetric flask, add 1.0 g of ceric sulfate, swirl to dissolve, dilute with 2 N sulfuric acid to volume, and mix.

2.1.2 Analysis

Samples: Standard solution and Sample solution

When the solvent front has moved about three-fourths the length of the plate, remove the plate from the chamber, and dry at 110° for 20 min. Allow to cool, spray with Spray reagent, and heat the plate at 110° for about 10 min.

Acceptance criteria: The principal spot from the Sample solution corresponds in color, size, and R value to that from the Standard solution. F

2.2 B. Procedure

Sodium hydroxide solution: 42 mg/mL of sodium hydroxide

Ammonium chloride solution: 107 mg/mL of ammonium chloride

Glycerin solution: A mixture of glycerin and water (85:15)

Sodium sulfide solution: Dissolve 12 g of sodium sulfide with heating in a 45-mL mixture of Glycerin solution and water (29:10), allow to cool, and dilute with the same mixture of solvents to 100 mL. The solution should be colorless.

Sample solution: Shake and sonicate the amount of powdered Tablets with the necessary volume of water to obtain a solution containing 100 mg/mL of zinc gluconate. Heat in a water bath at 60°, if necessary, and filter.

Analysis: To 5 mL of the Sample solution add 0.2 mL of Sodium hydroxide solution, add an additional 2 mL of Sodium hydroxide solution, and add 10 mL of Ammonium chloride solution. Add 0.1 mL of Sodium sulfide solution.

Acceptance criteria: A white precipitate is formed after the first addition of Sodium hydroxide solution. The precipitate dissolves after the second addition of Sodium hydroxide solution. The solution remains clear after addition of Ammonium chloride solution, and a white precipitate forms after addition of Sodium sulfide solution.

3 STRENGTH

Procedure

Sample solution: Weigh and finely powder NLT 20 Tablets. Weigh a portion of the powder, equivalent to about 80 mg of zinc, transfer to a suitable crucible, and ignite, gently at first, until free from carbon. Cool the crucible, add 25 mL of water and 5 mL of hydrochloric acid, and stir. Heat on a steam bath for 5 min, and filter, rinsing the filter with several portions of water. Dilute the combined filtrate and washes with water to about 100 mL.

Analysis: Add ammonia–ammonium chloride buffer TS until the solution is neutral to litmus. Add 5 mL of ammonia–ammonium chloride buffer TS and 0.1 mL of eriochrome black TS, and titrate with 0.05 M edetate disodium VS to a blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 3.27 mg of Zn or 22.78 mg of zinc gluconate (C₁₂H₂₂O₁₄Zn).

Acceptance criteria: 93.0%–107.0%

4 PERFORMANCE TESTS

Disintegration 〈701〉: For Tablets intended to be mixed with water prior to intake as oral liquids

Time: NMT 60 s

Disintegration and Dissolution of Dietary Supplements 〈2040〉: For Tablets not to be mixed with water prior to ingestion Medium: Hydrochloric acid 0.01 N; 900 mL

Apparatus 2: 50 rpm

Time: 45 min

Analysis: Determine the amount of C₁₂H₂₂O₁₄Zn dissolved, employing atomic absorption spectrophotometry at the resonance emission line for zinc, at 213.8 nm, on filtered portions of the solution under test, suitably diluted with water, in comparison with a standard solution having a known concentration of zinc in the same Medium.

Tolerances: NLT 75% of the labeled amount of C₁₂H₂₂O₁₄Zn is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and storage: Preserve in tight containers, protected from light.

Labeling: Label the Tablets in terms of elemental zinc, and also in terms of zinc gluconate (C₁₂H₂₂O₁₄Zn). The labeling indicates whether the Tablets are intended to be mixed with water before intake.

USP Reference Standards 〈11〉

USP Potassium Gluconate RS