A: Ignite about 200mg at a temperature not above 600,in order to remove all organic matter,cool,dissolve the residue in 10mLof water,and filter:the filtrate responds to the tests for Potassium á191ñand for Chloride á191ñ.

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

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

Standard preparations— To separate 200-mLvolumetric flasks transfer 19.0mLand 25.0mL,respectively,of the Potassium stock solution,dilute with water to volume,and mix.The Standard preparationscontain 95.0µg and 125.0µg 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 20containers of Potassium Gluconate and Potassium Chloride for Oral Solution.Transfer an accurately weighed portion of the powder,equivalent to about 782mg (20mEq)of potassium,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 7.0mLof this stock solution to a 500-mLvolumetric 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 780mg (20mEq)of potassium,to a 100-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.Transfer 7.0mLof this stock solution to a 500-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the resonance line of 766.5nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ)equipped with a potassium hollow-cathode lamp and an air–acetylene flame,using water as the blank.Plot the absorbances of the Standard preparationsversus 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 0.02558mEq.

Ionic strength adjusting solution— Use 5Msodium nitrate.

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

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