For tablets labeled solely for veterinary use : 30 minutes.

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C10H21N3O·C6H8O7 dissolved as directed in the Assay, preparing test solutions by quantitatively diluting filtered portions of the solution under test with phosphate buffer (1:1) containing 62.48 g of monobasic potassium phosphate in 1000 mL of water.

Tolerances— Not less than 75% (Q) of the labeled amount of C10H21N3O·C6H8O7 is dissolved in 45 minutes.

Phosphate buffer, Mobile phase, and Chromatographic system— Proceed as directed in the Assay under Diethylcarbamazine Citrate.

Citric acid solution— Prepare a solution of citric acid in Phosphate buffer containing 2 mg per mL.

Standard solution— Prepare a solution of USP Diethylcarbamazine Citrate RS in Phosphate buffer having a known concentration of about 0.003 mg per mL.

Test solution— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 300 mg of diethylcarbamazine citrate, to a 100-mL volumetric flask, dilute with Phosphate buffer to volume, and mix. Filter or centrifuge, and use the clear filtrate or supernatant.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution, the Test solution, and the Citric acid solution into the chromatograph, record the chromatograms, and measure the responses for all the peaks. Calculate the percentage of each impurity in the portion Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Diethylcarbamazine Citrate RS in the Standard solution; ri is the peak response for each impurity obtained from the Test solution, disregarding any peak having a retention time corresponding to that of the main peak in the chromatogram obtained from the Citric acid solution; and rS is the peak response obtained from the Standard solution. Not more than 0.1% of any individual impurity is found.

Phosphate buffer, Mobile phase, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Diethylcarbamazine Citrate.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 5 mg of diethylcarbamazine citrate, to a 50-mL volumetric flask, dissolve in and dilute with Phosphate buffer to volume, and mix.

Procedure— Proceed as directed in the Assay under Diethylcarbamazine Citrate. Calculate the quantity, in mg, of diethylcarbamazine citrate (C10H21N3O·C6H8O7) in the portion of Tablets taken by the formula: in which the terms are as defined therein.