Medium: 0.01 N hydrochloric acid; 900 mL.

Apparatus 1: 100 rpm.

Time: 15 minutes.

Procedure— Determine the amount of C10H16N6S dissolved by employing UV absorption at the wavelength of maximum absorbance at about 218 nm on filtered portions of the solution under test, suitably diluted with Dissolution Medium, in comparison with a Standard solution having a known concentration of USP Cimetidine RS in the same Medium.

Tolerances— Not less than 80% (Q) of the labeled amount of C10H16N6S is dissolved in 15 minutes.

(Official January 1, 2007)

Mobile phase , Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Cimetidine.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of Cimetidine, to a 250-mL volumetric flask. Add 50 mL of methanol, shake for 2 minutes, add 40 mL of water, sonicate for 15 minutes, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 200-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Procedure— Separately inject equal volumes (about 50 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 mg, of cimetidine (C10H16N6S) in the portion of Tablets taken by the formula: in which the terms are as defined in the Assay under Cimetidine.