0.1 M Barium acetate buffer, pH 5.0; Staining reagent; and Procedure— Proceed as directed in Electrophoretic purity under Chondroitin Sulfate Sodium.

Standard solution— Use the Standard solution of middle concentration in the test for Content of chondroitin sulfate sodium.

Test solution— Prepare as directed in the test for Content of chondroitin sulfate sodium. The principal spot obtained from the Test solution has the same migration as the principal spot obtained from the Standard solution.

Medium: water; 900 mL.

Apparatus 2: 75 rpm.

Time: 60 minutes.

Cetylpyridinium chloride solution, Standard solutions, and Test solution— Prepare as directed in the test for Content of chondroitin sulfate sodium under Chondroitin Sulfate Sodium.

Procedure— Proceed as directed in the test for Content of chondroitin sulfate sodium, adjusting the volume of the aliquot and the concentrations of the Standard solutions, if necessary. Calculate the quantity, in mg, of chondroitin sulfate sodium dissolved by the formula: in which C is the concentration, in mg per mL, of chondroitin sulfate sodium in the solution under test.

Tolerances— Not less than 75% of the labeled amount of chondroitin sulfate sodium is dissolved in 60 minutes.

Cetylpyridinium chloride solution— Prepare a solution of cetylpyridinium chloride in water having a concentration of about 1 mg per mL.

Diluent— Weigh about 297 mg of monobasic potassium phosphate, 492 mg of dibasic potassium phosphate, and 250 mg of polysorbate 80, and transfer into a 1-L beaker. Dissolve in approximately 900 mL of water, and adjust with potassium hydroxide or phosphoric acid to a pH of 7.0±0.2. Dilute with water to 1 L, and mix thoroughly.

Standard solutions— Prepare as directed in the test for Content of chondroitin sulfate sodium under Chondroitin Sulfate Sodium.

Test solution— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of chondroitin sulfate sodium, to a 100-mL volumetric flask, add 60 mL of water, and shake to suspend the powder in solution. Sonicate in a 65 water bath for 20 minutes. Remove from the bath, stir or shake for 5 minutes, dilute with water to volume, and centrifuge or pass through a suitable filter.

Procedure— Separately transfer 5.0 mL of each Standard solution and the Test solution to separate titration vessels, and add about 25 mL of Diluent to each. Stir until a steady reading is obtained using a phototrode to determine the endpoint turbidimetrically, either at 420, 550, or 660 nm. Set the instrument to zero in absorbance mode. From a linear regression equation calculated using the volumes of Cetylpyridinium chloride solution consumed, and the mass, in mg, of USP Chondroitin Sulfate Sodium RS, determine the mass of chondroitin sulfate sodium in the aliquot of the Test solution taken. Calculate the amount, in mg, of chondroitin sulfate sodium in the portion of Tablets taken by the formula: in which M is the mass of chondroitin sulfate sodium in the aliquot of the Test solution.