Sodium Citrate
(soe' dee um si' trate).
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C6H5Na3O7 258.07
1,2,3-Propanetricarboxylic acid, 2-hydroxy-, trisodium salt;    
Trisodium citrate (anhydrous)     [68-04-2].
C6H5Na3O7·2H2O 294.10
Trisodium citrate dihydrate     [6132-04-3].
Sodium Citrate is anhydrous or contains two molecules of water of hydration. It contains NLT 99.0% and NMT 100.5% of C6H5Na3O7, calculated on the anhydrous basis.
•  A. Identification Tests—General, Sodium 191
Sample solution:  50 mg/mL
Acceptance criteria:  Meets the requirements
•  B. Identification Tests—General, Citrate 191
Sample solution:  50 mg/mL
Acceptance criteria:  Meets the requirements
•  C. Upon ignition, it yields an alkaline residue that effervesces when treated with 3 N hydrochloric acid.
•  Procedure
Sample:  Add 100 mL of glacial acetic acid to 350 mg of Sodium Citrate (previously dried at 180 for 18 h) in a 250-mL beaker. Stir until completely dissolved.
Analysis:  Titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction (see Titrimetry 541). Each mL of 0.1 N perchloric acid is equivalent to 8.602 mg of C6H5Na3O7.
Acceptance criteria:  99.0%–100.5% on the anhydrous basis
•  Heavy Metals 231
[Note—Use 50-mL color comparison tubes for preparing the Standard preparation, Test preparation, and Monitor preparation. ]
Standard preparation:  1.0 mL of Standard Lead Solution and 11 mL of water
Test stock preparation:  88 mg/mL of anhydrous sodium citrate in water
Test preparation:  12 mL of the Test stock preparation
Monitor preparation:  11 mL of the Test stock preparation and 1.0 mL of Standard Lead Solution
Analysis:  Proceed as directed in the chapter for Procedure, omitting the dilution to 50 mL.
Acceptance criteria:  NMT 10 ppm
•  Tartrate
Analysis:  To a solution of 1 g in 2 mL of water in a test tube add 1 mL of potassium acetate TS and 1 mL of 6 N acetic acid. Rub the wall of the tube with a glass rod.
Acceptance criteria:  No crystalline precipitate is formed.
•  Alkalinity
Sample solution:  1.0 g in 20 mL of water
Acceptance criteria:  The Sample solution is alkaline to litmus paper, but after the addition of 0.20 mL of 0.10 N sulfuric acid, no pink color is produced by 1 drop of phenolphthalein TS.
•  Water Determination, Method III 921: Dry a sample at 180 for 18 h: the anhydrous form loses NMT 1.0% of its weight; the hydrous form loses 10.0%–13.0% of its weight.
•  Packaging and Storage: Preserve in tight containers.
•  Labeling: Label it to indicate whether it is anhydrous or hydrous.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Sujatha Ramakrishna, Ph.D.
Senior Scientific Liaison
(SM22010) Monographs - Small Molecules 2
USP35–NF30 Page 4657