Ferrous Gluconate Capsules
DEFINITION
Ferrous Gluconate Capsules 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 the contents of the Capsules
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.
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
Buffer:
Dissolve 3.0 g of sodium acetate in 50 mL of water. Add 2.0 mL of glacial acetic acid, dilute with water to 200 mL, and mix. This Buffer has a pH of 4.6.
Color reagent solution:
Dissolve 400 mg of 2,2¢-bipyridine in 100 mL of water, using heat if necessary, to dissolve. Cool, and filter.
Standard stock solution:
7.022 mg/mL of ferrous ammonium sulfate hexahydrate [Fe(NH4)2(SO4)2·6H2O] in water, equivalent to 1000 µg/mL of iron (Fe)
Standard solution:
100 µg/mL of iron (Fe) in 0.1 N sulfuric acid from Standard stock solution
Sample solution
For hard gelatin capsules:
Transfer, as completely as possible, the contents of NLT 20 Capsules to a suitable tared container. Mix and finely powder the combined contents, and transfer a weighed portion of the powder, equivalent to 430 mg of ferrous gluconate dihydrate, to a 500-mL volumetric flask. Add 300 mL of water, heating on a steam bath if necessary to dissolve. Cool, and dilute with water to volume.
For soft gelatin capsules:
Place a number of Capsules, equivalent to 430 mg of ferrous gluconate dihydrate, in a 500-mL volumetric flask. Add 300 mL of water, heating on a steam bath to dissolve the Capsules. Cool, and dilute with water to volume.
Instrumental conditions
Mode:
UV-Vis
Analytical wavelength:
522 nm
Cell:
1 cm
Analysis
Samples:
Standard solution and Sample solution
Transfer 3.0 mL of the Sample solution to a 100-mL volumetric flask, and add, in the order named, 70 mL of Buffer, 10.0 mL of 100 mg/mL of sodium thiosulfate solution, and 5.0 mL of Color reagent solution, with mixing following each addition. Heat for 60 min on a steam bath, cool, dilute with Buffer to volume, and filter. Prepare reagent blanks for the Standard solution and the Sample solution by repeating the above procedure, omitting the addition of 5.0 mL of Color reagent solution.
Concomitantly determine the absorbances of the reacted solutions against the corresponding reagent blanks.
Calculate the percentage of the labeled amount of ferrous gluconate dihydrate (C12H22FeO14·2H2O) in the portion of Capsules taken:
Result = (AU/AS) × (CS/CU) × (Mr/Ar) × 100
| AU | = | = absorbance of the Sample solution corrected by the absorbance of its reagent blank |
| AS | = | = absorbance of the Standard solution corrected by the absorbance of its reagent blank |
| CS | = | = concentration of iron in the Standard solution (µg/mL) |
| CU | = | = nominal concentration of ferrous gluconate dihydrate in the Sample solution (µg/mL) |
| Mr | = | = molecular weight of ferrous gluconate dihydrate, 482.17 |
| Ar | = | = atomic weight of iron, 55.85 |
Acceptance criteria:
93.0%–107.0%
PERFORMANCE TESTS
• Dissolution 
711
711
Medium:
0.1 N hydrochloric acid; 900 mL
Apparatus 1:
100 rpm
Time:
45 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/Capsule) |
Tolerances:
NLT 75% (Q) of the labeled amount of ferrous gluconate dihydrate (C12H22FeO14·2H2O) is dissolved.
• Uniformity of Dosage Units 905:
Meet the requirements
905:
Meet the requirements
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers.
• Labeling:
Label the Capsules in terms of the content of ferrous gluconate dihydrate (C12H22FeO14·2H2O) and in terms of the content of elemental iron.
• USP Reference Standards 11
11
USP Potassium Gluconate RS 
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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 3176