A: It responds to the flame tests for Sodium 191 and Potassium 191, and to the tests for Magnesium 191 and Chloride 191.

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 preparation corresponds to that of the Standard preparation, obtained as directed in the Assay for gluconate.

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

(Official January 1, 2007)

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

Assay preparation— Transfer 5.0 mL of Injection to a 500-mL volumetric flask, dilute with Internal standard solution to volume, and mix.

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

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

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

Blank solution— Transfer 5.0 mL of Lanthanum chloride solution to a 100-mL volumetric flask, dilute with Dilute hydrochloric acid to volume, and mix.

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

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

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

Procedure— Concomitantly determine the absorbances of the Standard preparations and the Assay preparation at the magnesium emission line at 285.2 nm, with an atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering 851) equipped with a magnesium hollow-cathode lamp and an air–acetylene flame, using the Blank solution as the blank. Plot the absorbances of the Standard preparations versus 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 mL of the Injection taken by the formula: in which V is the volume, in mL, of Injection taken to prepare the Assay preparation.

Mobile phase— Prepare a filtered and degassed solution of 0.05 N sulfuric acid. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 210-nm detector, a 4.6-mm × 3-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 0.8 mL per 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 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mEq per L, of acetate (C2H3O2) in the Injection taken by the formula: in which C is the concentration, in mg per mL, of sodium acetate trihydrate in the Standard preparation; 136.08 is the molecular weight of sodium acetate trihydrate; L is the labeled quantity, in mEq per L, of acetate in the Injection; D is the quantity, in mEq per mL, of acetate in the Assay preparation, based on the labeled quantity and the extent of dilution; and rU and rS are the acetate peak responses obtained from the Assay preparation and the Standard preparation, respectively.

Mobile phase— Prepare a filtered and degassed solution of 0.05 N sulfuric acid. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 210-nm detector, a 4.6-mm × 3-cm guard column containing packing L17, and a 7.8-mm × 30-cm analytical column containing packing L17. The flow rate is about 0.8 mL per 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 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mEq per L, of gluconate (C6H11O7) in the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Potassium Gluconate RS in the Standard preparation; 234.25 is the molecular weight of anhydrous potassium gluconate; L is the labeled quantity, in mEq per L, of gluconate in the Injection; D is the quantity, in mEq per mL, of gluconate in the Assay preparation, based on the labeled quantity and the extent of dilution; and rU and rS are the gluconate peak responses obtained from the Assay preparation and the Standard preparation, respectively.

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

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

Sodium sulfite solution— Dissolve 1 g of sodium sulfite in water to make 5 mL of solution. [NOTE—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 0.11 mg per mL.

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

Blank— Use water.

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