Magnesium 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)

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1 DEFINITION

Magnesium Gluconate Tablets contain NLT 95.0% and NMT 105.0% of the labeled amount of magnesium gluconate (C₁₂H₂₂MgO₁₄).

2 IDENTIFICATION

A. Identification Tests—General, Magnesium〈191〉

Sample solution: A filtered solution in water from powdered Tablets, equivalent to 100 mg/mL of magnesium gluconate

Acceptance criteria: Meet the requirements

B. Thin-Layer Chromatographic Identification Test

Standard solution: 10 mg/mL of USP Potassium Gluconate RS

Sample solution: Equivalent to 10 mg/mL of magnesium gluconate from a dilution of the Sample solution obtained for the Identification test A

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, ethyl acetate, ammonium hydroxide, and water (50:10:10:30)

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

Analysis

Samples: Standard solution and Sample solution

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

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

3 ASSAY

Procedure

Sample: A portion of the powder from NLT 20 finely powdered Tablets, equivalent to 800 mg of magnesium gluconate

Blank: Proceed as directed in the Analysis without the Sample.

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.05 M edetate disodium VS

Endpoint detection: Visual

Analysis: Transfer the Sample to a 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. Filter, rinsing the filter with several portions of water. Dilute the combined filtrate and washings with water to 150 mL. Add ammonia–ammonium chloride buffer TS until the solution is neutral to litmus. Add an excess of 5mL of ammonia–ammonium chloride buffer TS and 0.1 mL of eriochrome black TS, and titrate with Titrant to a blue endpoint. Perform a

Blank determination.

Calculate the percentage of the labeled amount of magnesium gluconate (C₁₂H₂₂MgO₁₄) in the portion of Tablets taken:

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

V_S = Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL)

M = actual molarity of the Titrant (mM/mL)

F = equivalency factor, 414.6 mg/mM

W = nominal amount of magnesium gluconate in the Sample taken (mg)

Acceptance criteria: 95.0%–105.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Medium: Water; 900 mL

Apparatus 2: 50 rpm

Time: 30 min

Standard solution: Solution having a known concentration of magnesium in the Medium

Sample solution: Filtered portion of the solution under test, suitably diluted with the Medium if necessary

Instrumental conditions

(See Atomic Absorption Spectroscopy 〈852〉.)

Mode: Atomic absorption spectrophotometry

Analytical wavelength: 285.2 nm

Lamp: Magnesium hollow-cathode

Flame: Air–acetylene

Analysis

Samples: Standard solution and Sample solution

Determine the concentration of magnesium (Mg) in the Sample solution in comparison with a Standard solution.

Calculate the percentage of the labeled amount of magnesium gluconate (C₁₂H₂₂MgO₁₄) dissolved:

Result = (C × D × V/L) × (M_r/A_r) × 100

C = determined concentration of magnesium in the Sample solution (mg/mL)

D = dilution factor for the Sample solution

V = volume of Medium, 900 mL

L = label amount of magnesium gluconate (mg/Tablet)

M_r = molecular weight of magnesium gluconate, 414.60

A_r = atomic weight of magnesium, 24.31

Tolerances: NLT 80.0% (Q) of the labeled amount of magnesium gluconate (C₁₂H₂₂MgO₁₄) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Potassium Gluconate RS