Add the following:

A: Powder 5 Tablets, mix with 20 mL of water, and filter: the filtrate responds to the tests for Potassium 191.

B: A portion of powdered Tablets containing about 50 mg of potassium citrate responds to the test for Citrate 191, 20 mL of the mixture of pyridine and acetic anhydride being used.

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Times: 30 minutes, 1 hour, and 3 hours.

Potassium stock solution and Standard preparation—Prepare as directed in the Assay under Potassium Chloride Oral Solution.

Procedure— Filter the solution under test, and dilute quantitatively with Medium to obtain a test solution containing about 60 µg of potassium citrate per mL. Transfer 5.0 mL of the test solution to a 100-mL volumetric flask, add 2.0 mL of sodium chloride solution (1 in 5) and 1.0 mL of hydrochloric acid, dilute with water to volume, mix, and proceed as directed for Procedure in the Assay under Potassium Chloride Oral Solution. Calculate the quantity, in mg, of C6H5K3O7 dissolved by the formula: in which F is the extent of dilution of the solution under test; 2.612 is the ratio of the molecular weight of anhydrous potassium citrate to three times the atomic weight of potassium; and C is the concentration, in µg per mL, of potassium in the test solution.

Tolerances— The percentages of the labeled amount of C6H5K3O7 dissolved from the Tablets are not more than 45% (Q) in 30 minutes, not more than 60% (Q¢) in 1 hour, and not less than 80% (Q¢¢) in 3 hours. The requirements are met if the quantities dissolved from the Tablets tested conform to the accompanying table instead of the table shown under Dissolution 711.

Stage	Number Tested	Acceptance Criteria
S1	6	Each unit is within the range between Q ± 10% and Q¢ ± 10%, and is not less than Q¢¢ + 5% at the stated Times.
S2	6	Average of 12 units (S1 + S2) is within the range between Q ± 10% and Q¢ ± 10% and is not less than Q¢¢; no unit is outside the range between Q ± 15% and Q¢ ± 15%, and no unit is less than Q¢¢ 5% at the stated Times.
S3	12	Average of 24 units (S1 + S2 + S3) is within the range between Q ± 10% and Q¢ ± 10% and is not less than Q¢¢; not more than 1 unit is outside the range between Q ± 15%, not more than 1 unit is outside the range between Q¢ ± 15%, and not more than 1 unit is less than Q¢¢ 5% at the stated Times.

Potassium stock solution and Standard preparations— Prepare as directed in the Assay under Potassium Chloride Oral Solution.

Assay preparation— Transfer 3.0 mL of the clear filtrate, reserved from the Assay, to a 100-mL volumetric flask, add 2.0 mL of sodium chloride solution (1 in 5) and 1.0 mL of hydrochloric acid, dilute with water to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Potassium Chloride Oral Solution. Calculate the quantity, in mg, of potassium (K) in the portion of Tablets taken by the formula: in which C is as defined therein: the quantity, in mg, of potassium found in the portion of Tablets taken is not less than 36.4% and not more than 40.2% of the quantity, in mg, of potassium citrate in the portion of Tablets taken, as determined in the Assay.

(Official January 1, 2007)

Standard preparation— Dissolve a suitable quantity of citric acid, previously dried at 90 for 3 hours and accurately weighed, in water to obtain a solution having a known concentration of about 1.0 mg of anhydrous citric acid per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 200 mg of potassium citrate, to a 1000-mL volumetric flask, add about 300 mL of hot water, and shake by mechanical means for 15 minutes. Allow to cool, dilute with water to volume, and mix. Filter, discarding the first 30 mL of the filtrate. Transfer 20.0 mL of the clear filtrate to a 25-mL volumetric flask, dilute with water to volume, and mix. [NOTE—Reserve the remaining filtrate for the test for Potassium content.]

Standard curve— Pipet aliquots of 8, 9, 10, 11, and 12 mL, respectively, of the Standard preparation into separate 100-mL volumetric flasks, dilute with water to volume, and mix. These solutions contain about 0.08, 0.09, 0.10, 0.11, and 0.12 mg of anhydrous citric acid per mL, respectively. Continue as directed for Procedure. Plot the resultant absorbances versus the respective concentrations, in mg per mL, of the standard solutions.

Procedure— Pipet 1 mL of the Assay preparation into a suitable test tube. To a second test tube add 1.0 mL of water to serve as a reference blank. To each tube add 1.3 mL of pyridine, and mix by swirling. To one tube at a time add 5.7 mL of acetic anhydride, and mix, using a rotary vortex stirrer. Immediately place in a water bath maintained at 31 ± 1.0, and allow the color to develop for 33 ± 1 minutes. Determine the absorbance against the reference blank in 2.5-cm cells at 425 nm, taking care to measure the absorbance of each solution at the same elapsed time from mixing. Calculate the quantity, in mg, of potassium citrate (C6H5K3O7) in the portion of Tablets taken by the formula: in which 306.40 and 192.13 are the molecular weights of anhydrous potassium citrate and anhydrous citric acid, respectively; and C is the concentration, in mg per mL, of anhydrous citric acid read from the Standard curve.

Change to read:

Mobile phase, Standard Preparation 1, and Chromatographic System— Proceed as directed under Assay for Citric Acid/Citrate and Phosphate 345.USP29

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 200 mg of potassium citrate, to a 1000-mL volumetric flask, add about 300 mL of hot water, and shake by mechanical means for 15 minutes. Allow to cool, dilute with water to volume, and mix. Filter, discarding the first 30 mL of the filtrate. Transfer an aliquot of the clear filtrate into a suitable volumetric flask, and dilute with water and freshly prepared sodium hydroxide solution to obtain a solution containing about 20 µg per mL of citrate in 1 mM sodium hydroxide.USP29 [NOTE—Reserve the remaining filtrate for the test for Potassium content.]

Procedure— Proceed as directed for Procedure under 345, and calculate the quantity, in mg, of potassium citrate (C6H5K3O7) in the portion of Tablets taken by the formula: in which 306.39 is the molecular weight of potassium citrate; 189.10 is the molecular weight of citrate (C6H5O7); CS is the concentration, in µg per mL, of citrate in Standard Preparation 1; D is the dilution factor; and rU and rS are the citrate peak areas obtained from the Assay preparation and Standard Preparation 1, respectively.USP29