Medium: water; 900 mL.

Apparatus 2: 75 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C21H21ClN2O8 dissolved from UV absorption at the wavelength of maximum absorbance at about 274 nm on filtered portions of the solution under test, suitably diluted with Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Demeclocycline Hydrochloride RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of demeclocycline (C21H21ClN2O8) is dissolved in 45 minutes.

(Official January 1, 2007)

Mobile phase, Standard preparation, Resolution solution, and Chromatographic system— Prepare as directed in the Assay under Demeclocycline.

Assay preparation— Weigh and finely powder not fewer than 10 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 50 mg of demeclocycline hydrochloride (C21H21ClN2O8·HCl), to a 50-mL volumetric flask, dilute with 0.01 N hydrochloric acid to volume, and mix. Sonicate for 5 minutes, and centrifuge for 5 minutes. Pass a portion of the supernatant through a suitable filter of 1.5-µm or finer porosity, and use the clear filtrate as the Assay preparation.

Procedure— Proceed as directed for Procedure in the Assay under Demeclocycline. Calculate the quantity, in mg, of demeclocycline hydrochloride (C21H21ClN2O8·HCl) in the portion of Tablets taken by the formula: in which the terms are as defined therein.