Ferrous Gluconate Tablets
DEFINITION
Ferrous Gluconate Tablets contain NLT 93.0% and NMT 107.0% of the labeled amount of ferrous gluconate dihydrate (C12H22FeO14·2H2O).
IDENTIFICATION
•  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
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.
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 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 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.
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 
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 flask. Add 250 mg of zinc dust, close the flask 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 flask 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 = {[(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:  93.0%–107.0%
PERFORMANCE TESTS
•  Dissolution 711
Medium:  Simulated gastric fluid 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 
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 = (Mr/Ar) × (C × D × V/L) × 100
Mr== molecular weight of ferrous gluconate dihydrate, 482.17
Ar== 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
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 Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Natalia Davydova
Scientific Liaison
1-301-816-8328
(DS2010) Monographs - Dietary Supplements
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
USP35–NF30 Page 3178