Lithium Citrate
(lith' ee um sit' rate).
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C6H5Li3O7·4H2O 281.98

1,2,3-Propanetricarboxylic acid, 2-hydroxy-trilithium salt tetrahydrate.
Trilithium citrate tetrahydrate [6080-58-6].

Anhydrous 209.93 [919-16-4].
» Lithium Citrate contains not less than 98.0 percent and not more than 102.0 percent of C6H5Li3O7, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers.
USP Reference standards 11
USP Lithium Carbonate RS
A: When moistened with hydrochloric acid, it imparts an intense crimson color to a nonluminous flame.
B: It responds to the test for Citrate 191.
pH 791: between 7.0 and 10.0, in a solution (1 in 20).
Water, Method III 921 Dry it at 150 for 3 hours: it loses between 24.0% and 28.0% of its weight.
Carbonate— Add about 0.5 g to 5 mL of 6 N acetic acid: not more than a slight effervescence is produced.
Heavy metals 231 Dissolve 2.0 g in 2 mL of 0.1 N hydrochloric acid, and dilute with water to 25 mL: the limit is 0.001%.
Standard preparation— Transfer to a 100-mL volumetric flask about 30 mg of USP Lithium Carbonate RS, accurately weighed. Add about 20 mL of water and 0.5 mL of hydrochloric acid, shake until dissolved, dilute with water to volume, and mix. Pipet 20 mL of the resulting solution into a 1000-mL volumetric flask, add about 800 mL of water and 20 mL of a suitable surfactant solution, appropriately diluted, dilute with water to volume, and mix.
Assay preparation— Transfer about 800 mg of Lithium Citrate, accurately weighed, to a 1000-mL volumetric flask. Dissolve in water, add 0.5 mL of hydrochloric acid, dilute with water to volume, and mix. Pipet 20 mL of this solution into a 1000-mL volumetric flask, add about 800 mL of water and 20 mL of the surfactant solution, dilute with water to volume, and mix.
Procedure— Employ a suitable flame photometer, and adjust the instrument with the surfactant solution. Aspirate into the instrument the Standard preparation and the Assay preparation, and measure the emission at about 671 nm. Calculate the quantity, in mg, of C6H5Li3O7 in the portion of Lithium Citrate taken by the formula:
(419.84 / 221.67)(50C)(A / S)
in which 419.84 is twice the molecular weight of anhydrous lithium citrate, 221.67 is three times the molecular weight of lithium carbonate; C is the concentration, in µg per mL, of USP Lithium Carbonate RS in the Standard preparation; and A and S are the photometer readings of the Assay preparation and the Standard preparation, respectively.
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Topic/Question Contact Expert Committee
Monograph Hariram Ramanathan, M.S.
Associate Scientific Liaison
(SM42010) Monographs - Small Molecules 4
Reference Standards RS Technical Services
USP35–NF30 Page 3702