A: It responds to the flame tests for Sodium á191ñand Potassium á191ñ,and to the tests for Magnesium á191ñand Chloride á191ñ.

B: The retention time of the acetate peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation obtained as directed in the Assay for acetate.

C: Where gluconate is purported to be present,the retention time of the gluconate peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationobtained as directed in the Assay for gluconate.

D: Where phosphate is purported to be present,add 5mLof the Injection and 1mLof ammonium molybdate TSto a test tube,and mix:a yellow precipitate,which is soluble in 6Nammonium hydroxide,is formed.

Internal standard solution,Potassium stock solution,Sodium stock solution,Stock standard preparation,and Standard preparation— Prepare as directed in the Assay for potassium and sodiumunder Potassium Chloride in Sodium Chloride Injection.

Assay preparation— Transfer 5.0mLof Injection to a 500-mLvolumetric flask,dilute with Internal standard solutionto volume,and mix.

Procedure— Proceed as directed for Procedurein the Assay for potassium and sodiumunder Potassium Chloride in Sodium Chloride Injection.Calculate the quantity,in mg,of potassium (K)in each mLof the Injection taken by the formula: in which the terms are as defined therein.Each mg of potassium is equivalent to 0.02558mEq of potassium.Calculate the quantity,in mg,of sodium (Na)in each mLof the Injection taken by the formula: in which the terms are as defined therein.Each mg of sodium is equivalent to 0.04350mEq of sodium.

Lanthanum chloride solution— Transfer 17.69g of lanthanum chloride to a 200-mLvolumetric flask,add 100mLof water,and carefully add 50mLof hydrochloric acid.Mix,and allow to cool.Dilute with water to volume,and mix.

Dilute hydrochloric acid— Prepare by mixing 678mLof hydrochloric acid with sufficient water to make 3000mL.

Blank solution— Transfer 5.0mLof Lanthanum chloride solutionto a 100-mLvolumetric flask,dilute with Dilute hydrochloric acidto volume,and mix.

Magnesium stock solution— Transfer 1.00g of magnesium metal to a 1000-mLvolumetric flask containing 10mLof water.Slowly add 10mLof hydrochloric acid,and swirl to dissolve the metal.Dilute with Dilute hydrochloric acidto volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with Dilute hydrochloric acidto volume,and mix.This solution contains 100µg of magnesium (Mg)per mL.

Standard preparations— To three separate 100-mLvolumetric flasks,each containing 5.0mLof Lanthanum chloride solution,add 10.0,15.0,and 20mL,respectively,of Magnesium stock solution.Dilute the contents of each flask with Dilute hydrochloric acidto volume,and mix.These three solutions contain 10.0,15.0,and 20.0µg,respectively,of magnesium (Mg)per mL.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 20mg (1.65mEq)of magnesium,to a 1000-mLvolumetric flask containing 50.0mLof Lanthanum chloride solution.Dilute the contents of the flask with Dilute hydrochloric acidto volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the magnesium emission line at 285.2nm,with an atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ)equipped with a magnesium hollow-cathode lamp and an air–acetylene flame,using the Blank solutionas the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of magnesium,and draw the straight line best fitting the three plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of magnesium in the Assay preparation.Calculate the quantity,in µg,of magnesium (Mg)in each mLof the Injection taken by the formula: in which Vis the volume,in mL,of Injection taken to prepare the Assay preparation.

Mobile phase— Prepare a filtered and degassed solution of 0.05Nsulfuric acid.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of sodium acetate trihydrate in water to obtain a Standard preparationhaving a known concentration of about 1.2mg of sodium acetate trihydrate (about 0.0088mEq of acetate)per mL.

Assay preparation— Dilute an accurately measured volume of Injection quantitatively with water to obtain a solution containing about 0.0088mEq of acetate per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 210-nm detector,a 7.8-mm ×4-cm guard column containing packing L17,and a 7.8-mm ×30-cm analytical column containing packing L17.The column temperature is maintained at about 60.The flow rate is about 0.8mLper minute.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the tailing factor for the analyte peak is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mEq per liter,of acetate (C2H3O2)in the Injection taken by the formula: in which Cis the concentration,in mg per mL,of sodium acetate trihydrate in the Standard preparation;136.08is the molecular weight of sodium acetate trihydrate;Lis the labeled quantity,in mEq per liter,of acetate in the Injection;Dis the quantity,in mEq per mL,of acetate in the Assay preparation,based on the labeled quantity and the extent of dilution;and rUand rSare the acetate peak responses obtained from the Assay preparationand the Standard preparation,respectively.

Mobile phase— Prepare a filtered and degassed solution of 0.05Nsulfuric acid.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Potassium Gluconate RSin water to obtain a Standard preparationhaving a known concentration of about 1mg of USP Potassium Gluconate RS(about 0.0043mEq of gluconate)per mL.

Assay preparation— Dilute an accurately measured volume of Injection quantitatively with water to obtain a solution containing about 0.004mEq of gluconate per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 210-nm detector,a 7.8-mm ×4-cm guard column containing packing L17,and a 7.8-mm ×30-cm analytical column containing packing L17,and maintained at about 60.The flow rate is about 0.8mLper minute.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the tailing factor for the analyte peak is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mEq per liter,of gluconate (C6H11O7)in the Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Potassium Gluconate RSin the Standard preparation,234.25is the molecular weight of anhydrous potassium gluconate;Lis the labeled quantity,in mEq per liter,of gluconate in the Injection;Dis the quantity,in mEq per mL,of gluconate in the Assay preparation,based on the labeled quantity and the extent of dilution;and rUand rSare the gluconate peak responses obtained from the Assay preparationand the Standard preparation,respectively.

Ammonium molybdate solution— Transfer 25g of ammonium molybdate to a 500-mLvolumetric flask,add about 300mLof water,and swirl to effect solution.Add 75mLof sulfuric acid,and swirl.Allow to cool,dilute with water to volume,and mix.

Hydroquinone solution— Dissolve 0.5g of hydroquinone in 100mLof water,add 1drop of sulfuric acid,and mix.Prepare this solution fresh daily.

Sodium sulfite solution— Dissolve 1g of sodium sulfite in water to make 5mLof solution.Prepare this solution fresh daily.

Standard preparation— Dissolve an accurately weighed quantity of monobasic potassium phosphate in water to obtain a solution having a known concentration of about 0.11mg per mL.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 4mg (0.126mEq)of phosphate,to a 50-mLvolumetric flask,dilute with water to volume,and mix.

Blank— Use water.

Procedure— Transfer 2.0mLeach of the Standard preparation,the Assay preparation,and the Blankto separate test tubes.To each test tube add 1.0mLof Ammonium molybdate solution,mix,and allow to stand for 3minutes.Add 1.0mLof Hydroquinone solution,and mix.Add 1.0mLof Sodium sulfite solution,mix,and allow to stand for 30minutes.Concomitantly determine the absorbances of the Assay preparationand the Standard preparationat 640nm,using water to zero the instrument.Calculate the quantity,in mg,of phosphate (PO4)in each mLof the Injection taken by the formula: in which 94.97is the formula weight of phosphate (PO4);136.09is the molecular weight of monobasic potassium phosphate;Cis the concentration,in mg per mL,of monobasic potassium phosphate in the Standard preparation;Vis the volume,in mL,of Injection taken;and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively,corrected for any absorbance of the solution from the Blank.