Magnesium Gluconate Tablets
Magnesium Gluconate Tablets contain NLT 95.0% and NMT 105.0% of the labeled amount of magnesium gluconate (C12H22MgO14).
•  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 
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.
•  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 
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 5 mL 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 = {[(VS VB) × M × F]/W} × 100
VS== Titrant volume consumed by the Sample (mL)
VB== 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%
•  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 
Mode: Atomic absorption spectrophotometry
Analytical wavelength: 285.2 nm
Lamp: Magnesium hollow-cathode
Flame: Air–acetylene
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) × (Mr/Ar) × 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)
Mr== molecular weight of magnesium gluconate, 414.60
Ar== 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
•  Packaging and Storage: Preserve in well-closed containers.
•  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/QuestionContactExpert Committee
MonographNatalia Davydova
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
711Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
(GCDF2010) General Chapters - Dosage Forms
Reference StandardsRS Technical Services
USP35–NF30 Page 3749