Ferrous 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

Ferrous Gluconate Tablets contain NLT 93.0% and NMT 107.0% of the labeled amount of ferrous gluconate dihydrate (C₁₂H₂₂FeO₁₄ · 2H₂O).

2 IDENTIFICATION

2.1 A. Thin-Layer Chromatography

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

Sample solution: A filtered solution in water, equivalent to 10 mg/mL of ferrous gluconate dihydrate from powdered Tablets

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, 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 ask. Add 1.0 g of ceric sulfate, swirl to dissolve, and dilute with 2 N sulfuric acid to volume.

2.1.2 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. F

2.2 B. Ferrous Ion

Sample solution: Equivalent to 5 mg/mL of ferrous gluconate dihydrate from a dilution of the Sample solution obtained in Identification test A Analysis: Add potassium ferricyanide TS to the Sample solution.

Acceptance criteria: The solution yields a dark blue precipitate.

3 ASSAY

Procedure

Sample: A portion of the powder from NLT 20 finely powdered Tablets, equivalent to 1.5 g of ferrous gluconate dihydrate Blank: Proceed as directed in the Analysis without the Sample.

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.1 N ceric sulfate VS

Indicator: Orthophenanthroline TS

Endpoint detection: Visual

Analysis: Dissolve the Sample in a mixture of 75 mL of water and 15 mL of 2 N sulfuric acid in a 300-mL conical ask. Add 250 mg of zinc dust, close the ask with a stopper containing a Bunsen valve, and allow to stand at room temperature for 20 min or until the solution becomes colorless. Pass the solution through a filtering crucible containing a thin layer of zinc dust, and wash the crucible and contents with 10 mL of 2 N sulfuric acid, followed by 10 mL of water.

[Note—Prepare and use the filtering crucible in a well-ventilated hood.]

Add orthophenanthroline TS, and immediately titrate the filtrate in the suction ask with Titrant until color change. Perform a Blank determination.

Calculate the percentage of the labeled amount of ferrous gluconate dihydrate (C₁₂H₂₂FeO₁₄ · 2H₂O) in the portion of Tablets taken:

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

V_S = Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL)

N = actual normality of the Titrant (mEq/mL)

F = equivalency factor, 482.2 mg/mEq

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

Acceptance criteria: 93.0%–107.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Medium: Simulated gastric uid TS; 900 mL

Apparatus 2: 150 rpm

Time: 80 min

Standard solution: Solution having a known concentration of iron 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: 248.3 nm

Lamp: Iron hollow-cathode

Flame: Air–acetylene

Analysis

Samples: Standard solution and Sample solution

Determine the concentration of iron (Fe) in the Sample solution in comparison with a Standard solution.

Calculate the percentage of the labeled amount of ferrous gluconate dihydrate (C₁₂H₂₂FeO₁₄ · 2H₂O) dissolved:

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

M_r = molecular weight of ferrous gluconate dihydrate, 482.17

A_r = atomic weight of iron, 55.85

C = measured concentration of iron in the Sample solution (mg/mL)

D = dilution factor for the Sample solution

V = volume of Medium, 900 mL

L = label amount of ferrous gluconate dihydrate (mg/Tablet)

Tolerances: NLT 80% (Q) of the labeled amount of ferrous gluconate dihydrate (C₁₂H₂₂FeO₁₄ · 2H₂O) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

Labeling: Label the Tablets in terms of the content of ferrous gluconate dihydrate (C₁₂H₂₂FeO₁₄ · 2H₂O) and in terms of the content of elemental iron.

USP Reference Standards 〈11〉

USP Potassium Gluconate RS.