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Lithium Citrate Syrup
(Current title—not to change until June 1,2005)
Monograph title change—to become official June 1,2005
See Lithium Oral Solution
»Lithium Citrate Syrup is prepared from Lithium Citrate or Lithium Hydroxide to which an excess of Citric Acid has been added.It contains not less than 90.0percent and not more than 110.0percent of the labeled amount of lithium (Li).
Packaging and storage—
Preserve in tight containers.
Identification—
A:
When diluted with an equal volume of 3Nhydrochloric acid,it imparts an intense crimson color to a nonluminous flame.
B:
It responds to the test for Citrate á191ñ.
pHá791ñ:
between 4.0and 5.0.
Assay—
Assay preparation—
Transfer an accurately measured volume of Syrup,equivalent to about 60mg of lithium,to a 1000-mLvolumetric flask,dilute with water to volume,and mix.Pipet 20mLof the resulting solution into a 1000-mLvolumetric flask,add about 950mLof water,2mLof 1Nhydrochloric acid,and 20mLof a surfactant solution,and mix.Adjust with 1Nhydrochloric acid or 1Nsodium hydroxide to the same pH(±0.1pHunit)as that of the Standard preparation,dilute with water to volume,and mix.
Procedure—
Employ a suitable flame photometer,and adjust the instrument with the surfactant solution.Aspirate into the photometer the Standard preparationand the Assay preparation,and measure the emission at about 671nm.Calculate the quantity,in mg,of lithium in each mLof the Syrup taken by the formula:
(13.88/73.89)(50C/V)(A/S),
in which 13.88is twice the atomic weight of lithium,73.89is the molecular weight of lithium carbonate;Cis the concentration,in µg per mL,of USP Lithium Carbonate RSin the Standard preparation;Vis the volume,in mL,of Syrup taken;and Aand Sare the photometer readings of the Assay preparationand the Standard preparation,respectively.
Auxiliary Information—
Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1144
Pharmacopeial Forum:Volume No.28(2)Page 314
Phone Number:1-301-816-8330
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