Ferrous Gluconate Oral Solution
Ferrous Gluconate Oral Solution contains NLT 94.0% and NMT 106.0% of the labeled amount of ferrous gluconate dihydrate (C12H22FeO14·2H2O).
•  A. Thin-Layer Chromatography
Standard solution:  10 mg/mL of USP Potassium Gluconate RS in water
Sample solution:  A filtered solution in water, equivalent to 10 mg/mL of ferrous gluconate dihydrate from Oral Solution
Chromatographic system 
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.
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 RF value to that of the Standard solution.
•  B. Ferrous Ion
Sample solution:  Equivalent to 5 mg/mL of ferrous gluconate dihydrate from a dilution in water 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.
•  Procedure
Sample:  An accurately measured volume of Oral Solution, equivalent to 1.2 g of ferrous gluconate dihydrate
Blank:  Proceed as directed in the Analysis without the Sample.
Titrimetric system 
Mode:  Direct titration
Titrant:  0.1 N ceric sulfate VS
Indicator:  Orthophenanthroline TS
Endpoint detection:  Visual
Analysis:  Dissolve the Sample in a cooled mixture of 80 mL of recently boiled water and 80 mL of 2 N sulfuric acid. Add orthophenanthroline TS, and immediately titrate with Titrant until a change in color. Perform a Blank determination.
Calculate the percentage of the labeled amount of ferrous gluconate dihydrate (C12H22FeO14·2H2O) in the portion of Oral Solution taken:
Result = {[(VS VB) × N × F]/W} × 100
VS== Titrant volume consumed by the Sample (mL)
VB== 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:  94.0%–106.0%
•  Alcohol Determination 611: 6.3%–7.7% of C2H5OH
•  pH 791: 3.4–3.8
•  Packaging and Storage: Preserve in tight, light-resistant containers.
•  Labeling: Label the Oral Solution 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 Click to View Structure
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Monograph Natalia Davydova
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
Reference Standards RS Technical Services
USP35–NF30 Page 3178
Pharmacopeial Forum: Volume No. 28(2) Page 297