A: It meets the requirements of the flame test for Sodium 191.

B: Add 2 mL of 15% potassium carbonate TS to 2 mL of Oral Solution, boil, and cool. Add 4 mL of potassium pyroantimonate TS: a dense precipitate is formed (presence of sodium).

C: To 2 mL of a dilution of Oral Solution (1 in 20) add 5 mL of sodium cobaltinitrite TS: a yellow precipitate is not formed immediately (absence of potassium).

D: It meets the requirements of the tests for Citrate 191, 3 to 5 drops of Oral Solution and 20 mL of the mixture of pyridine and acetic anhydride being used.

FOR ORAL SOLUTION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

FOR ORAL SOLUTION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.

(Official January 1, 2007)

Potassium stock solution, Sodium stock solution, Lithium diluent solution, and Standard preparation— Prepare as directed in the Assay for sodium and potassium under Tricitrates Oral Solution.

Assay preparation— Transfer an accurately measured volume of Oral Solution, equivalent to about 1 g of sodium citrate dihydrate, to a 100-mL volumetric flask, dilute with water to volume, and mix. Transfer 50 µL of this solution to a 10-mL volumetric flask, dilute with Lithium diluent solution to volume, and mix.

Procedure— Using a suitable flame photometer, adjusted to read zero with Lithium diluent solution, concomitantly determine the sodium flame emission readings for the Standard preparation and the Assay preparation at the wavelength of maximum emission at about 589 nm. Calculate the quantity, in g, of Na in each mL of Oral Solution taken by the formula: in which 14.61 is the weight, in g, of sodium chloride in the Sodium stock solution; V is the volume, in mL, of Oral Solution taken, 22.99 is the atomic weight of sodium; 58.44 is the molecular weight of sodium chloride; and RU,Na and RS,Na are the sodium emission readings obtained for the Assay preparation and the Standard preparation, respectively.

Cation-exchange column— Mix 10 g of styrene-divinylbenzene cation-exchange resin with 50 mL of water in a suitable beaker. Allow the resin to settle, and decant the supernatant until a slurry of resin remains. Pour the slurry into a 15-mm × 30-cm glass chromatographic tube (having a sealed-in, coarse-porosity fritted disk and fitted with a stopcock), and allow to settle as a homogeneous bed. Wash the resin bed with about 100 mL of water, closing the stopcock when the water level is about 2 mm above the resin bed.

Procedure— Transfer an accurately measured volume of Oral Solution, equivalent to about 1 g of sodium citrate dihydrate, to a 100-mL volumetric flask; dilute with water to volume; and mix. Pipet 5 mL of this solution carefully onto the top of the resin bed in the Cation-exchange column. Place a 250-mL conical flask below the column, open the stopcock, and allow to flow until the solution has entered the resin bed. Elute the column with 60 mL of water at a flow rate of about 5 mL per minute, collecting about 65 mL of the eluate. Add 5 drops of phenolphthalein TS to the eluate, swirl the flask, and titrate with 0.02 N sodium hydroxide VS. Record the buret reading, and calculate the volume (B) of 0.02 N sodium hydroxide consumed. Calculate the quantity, in mg, of sodium citrate dihydrate (C6H5Na3O7·2H2O) in each mL of the Oral Solution taken by the formula: in which 1.961 is the equivalent, in mg, of C6H5Na3O7·2H2O, of each mL of 0.02 N sodium hydroxide; V is the volume, in mL, of Oral Solution taken; 294.10 and 210.14 are the molecular weights of sodium citrate dihydrate and citric acid monohydrate, respectively; and C is the concentration, in mg per mL, of citric acid monohydrate in the Oral Suspension, as obtained in the Assay for citric acid.

1.401A(20/V),