Magnesium Citrate for Oral Solution
» Magnesium Citrate for Oral Solution, when constituted as directed in the labeling, yields a solution that contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of magnesium citrate (C12H10Mg3O14).
Packaging and storage— Preserve in tight containers.
Labeling— The label contains directions for constitution of the powder and states the equivalent amount of magnesium citrate (C12H10Mg3O14) in a given volume of the Oral Solution obtained after constitution.
(Official January 1, 2009)
Microbial enumeration tests 61 and Tests for specified microorganisms 62— It meets the requirements of the test for absence of Escherichia coli and Salmonella species.
Uniformity of dosage units 905: meets the requirements.
Content of anhydrous citric acid—
Cation-exchange column, Test solution, and Procedure— Proceed as directed in the test for Content of anhydrous citric acid under Magnesium Carbonate and Citric Acid for Oral Solution. The content of anhydrous citric acid is between 76.6% and 93.7% of the labeled amount of magnesium citrate.
(Official until January 1, 2009)
Content of anhydrous citric acid—
Mobile Phase, Standard Preparation 1, and Chromatographic System— Proceed as directed under Assay for Citric Acid/Citrate and Phosphate 345.
Assay preparation— Transfer an accurately measured volume of the constituted Oral Solution, equivalent to about 9 g of anhydrous citric acid into a suitable volumetric flask, and proceed as directed for Assay Preparation for Citric Acid/Citrate Assay under Assay for Citric Acid/Citrate and Phosphate 345.
Procedure— Proceed as directed for Procedure under 345, and calculate the quantity, in mg, of anhydrous citric acid (C6H8O7) in the volume of constituted Oral Solution taken by the formula:
0.001(192.12 / 189.10)CS D(rU / rS)
in which 192.12 is the molecular weight of anhydrous citric acid; 189.10 is the molecular weight of citrate (C6H5O7); CS is the concentration, in µg per mL, of citrate in Standard Preparation 1; D is the dilution factor; and rU and rS are the citrate peak areas obtained from the Assay preparation and Standard Preparation 1, respectively. The content of anhydrous citric acid is between 76.6% and 93.7% of the labeled amount of magnesium citrate.
(Official January 1, 2009)
Other requirements— Constitute Magnesium Citrate for Oral Solution as directed in the labeling: it responds to the Identification tests and meets the requirements for Chloride, Sulfate, and Tartaric acid under Magnesium Citrate Oral Solution.
Assay— Transfer an accurately measured volume of constituted Oral Solution, equivalent to about 18.7 g of magnesium citrate (C12H10Mg3O14), to a 1000-mL volumetric flask. Add 200 mL of 1 N hydrochloric acid, swirl, and allow to stand for about 10 minutes. Dilute with water to volume, and mix. Stir by mechanical means for about 30 minutes. Transfer 10.0 mL of this solution to a 250-mL beaker. Add 10 mL of ammonia–ammonium chloride buffer TS, 5 mL of triethanolamine, 0.3 mL of eriochrome black TS, and titrate with 0.05 M edetate disodium VS until the last hint of violet disappears (blue endpoint). Each mL of 0.05 M edetate disodium is equivalent to 7.520 mg of magnesium citrate (C12H10Mg3O14).
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Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Senior Scientist
1-301-816-8251		 (MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
Reference Standards Lili Wang, Technical Services Scientist
1-301-816-8129
RSTech@usp.org
61 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
1-301-816-8339		 (MSA05) Microbiology and Sterility Assurance
62 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
1-301-816-8339		 (MSA05) Microbiology and Sterility Assurance
USP32–NF27 Page 2833
Pharmacopeial Forum: Volume No. 31(2) Page 421