A: Ignite about 200 mg at a temperature not above 600, in order to remove all organic matter, cool, dissolve the residue in 10 mL of water, and filter: the filtrate responds to the tests for Potassium 191 and for Chloride 191.

B: A mineral oil dispersion of it exhibits an IR absorption maximum in the spectral region between 6.2 and 6.25 µm (carboxylic acid salt).

(Official January 1, 2007)

Potassium stock solution— Dissolve in water 0.9535 g of potassium chloride, previously dried at 105 for 2 hours. Transfer to a 500-mL volumetric flask, dilute with water to volume, and mix. This solution contains 1000 µg of potassium per mL.

Standard preparations— To separate 200-mL volumetric flasks transfer 19.0 mL and 25.0 mL, respectively, of the Potassium stock solution, dilute with water to volume, and mix. The Standard preparations contain 95.0 µg and 125.0 µg of potassium per mL, respectively.

Assay preparation 1 (where it is packaged in unit-dose containers)—Weigh and mix the contents of not less than 20 containers of Potassium Gluconate and Potassium Chloride for Oral Solution. Transfer an accurately weighed portion of the powder, equivalent to about 782 mg (20 mEq) of potassium, to a 100-mL volumetric flask, dilute with water to volume, and mix. Transfer 7.0 mL of this stock solution to a 500-mL volumetric flask, dilute with water to volume, and mix.

Assay preparation 2 (where it is packaged in multiple-unit containers)—Transfer an accurately weighed portion of Potassium Gluconate and Potassium Chloride for Oral Solution, equivalent to about 780 mg (20 mEq) of potassium, to a 100-mL volumetric flask, dissolve in water, dilute with water to volume, and mix. Transfer 7.0 mL of this stock solution to a 500-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparations and the Assay preparation at the resonance line of 766.5 nm, with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering 851) equipped with a potassium hollow-cathode lamp and an air–acetylene flame, using water as the blank. Plot the absorbances of the Standard preparations versus concentration, in µg per mL, of potassium. From the graph so obtained, determine the concentration, C, in µg per mL, of potassium in the Assay preparation. Calculate the quantity, in mg, of potassium in the portion of Potassium Gluconate and Potassium Chloride for Oral Solution taken by the formula: Each mg of potassium is equivalent to 0.02558 mEq.

Ionic strength adjusting solution— Use 5 M sodium nitrate.

Assay preparation 1 (where it is packaged in unit-dose containers)—Weigh and mix the contents of not less than 20 containers of Potassium Gluconate and Potassium Chloride for Oral Solution. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg (2.8 mEq) of chloride, to a suitable beaker.

Assay preparation 2 (where it is packaged in multiple-unit containers)—Transfer an accurately weighed portion of Potassium Gluconate and Potassium Chloride for Oral Solution, equivalent to about 100 mg (2.8 mEq) of chloride, to a suitable beaker.

Procedure— Add 2.0 mL of Ionic strength adjusting solution to Assay preparation 1 or Assay preparation 2, add water to make about 100 mL, and titrate with 0.1 N silver nitrate VS, determining the endpoint potentiometrically, using a silver-sulfide specific ion-selective electrode and a double-junction reference electrode containing potassium nitrate solution (1 in 10). Perform a blank determination, and make any necessary correction. Each mL of 0.1 N silver nitrate is equivalent to 3.545 mg of chloride (Cl). Each mg of chloride is equivalent to 0.0282 mEq of Cl.