Medium: pH 8.60 buffer, prepared by mixing 2.3 volumes of 0.2 M sodium hydroxide with 2.5 volumes of 0.2 M monobasic potassium phosphate and 2.0 volumes of methanol, cooling, mixing with water to obtain 10 volumes of solution, and adjusting, if necessary, by the addition of 1 N sodium hydroxide to a pH of 8.60 ± 0.05. The initial volume for the test is 900 mL.

Apparatus 2: 60 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C12H12N2O3 dissolved from UV absorbances at the wavelength of maximum absorbance at about 258 nm of filtered portions of the solution under test, suitably diluted with 0.01 N sodium hydroxide, if necessary, in comparison with a Standard solution of known concentration of USP Nalidixic Acid RS in 0.01 N sodium hydroxide, using as the blank a mixture of Medium and 0.01 N sodium hydroxide in the same proportions as present in the test solution.

Tolerances— Not less than 80% (Q) of the labeled amount of C12H12N2O3 is dissolved in 30 minutes.

(Official January 1, 2007)

Mobile phase, Internal standard solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Nalidixic Acid Oral Suspension.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 150 mg of nalidixic acid, to a 500-mL volumetric flask, add about 400 mL of methanol, and sonicate for about 30 minutes. Shake by mechanical means for about 30 minutes, sonicate again for about 30 minutes, dilute with methanol to volume, mix, and filter. Transfer 3.0 mL of the clear filtrate and 1.0 mL of Internal standard solution to a 25-mL volumetric flask, dilute with methanol to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Nalidixic Acid Oral Suspension. Calculate the quantity, in mg, of C12H12N2O3 in the portion of Tablets taken by the formula: in which the terms are as defined therein.