Medium: water;900mL.

Apparatus 2: 75rpm,the distance between the blade and the inside bottom of the flask being maintained at 4.5±0.5cm during the test.

Time: 90minutes.

Procedure— Determine the amount of C22H24N2O8dissolved from UVabsorbances at the wavelength of maximum absorbance at about 276nm of filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Doxycycline Hyclate RSin the same medium.

Tolerances— Not less than 85%(Q)of the labeled amount of C22H24N2O8is dissolved in 90minutes.

Mobile phase,Diluent,Resolution solution,Standard preparation,andChromatographic system— Proceed as directed in the Assayunder Doxycycline Hyclate.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 100mg of doxycycline,to a 100-mLvolumetric flask,add about 75mLof Diluent,sonicate for 5minutes,shake for 15minutes,dilute with Diluentto volume,and mix.Filter through a membrane filter of 0.5µm or finer porosity.

Procedure— Proceed as directed for Procedurein the Assayunder Doxycycline Hyclate.Calculate the quantity,in mg,of doxycycline (C22H24N2O8)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Doxycycline Hyclate RSin the Standard preparation,Pis the designated potency,in µg of doxycycline per mg,of USP Doxycycline Hyclate RS,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.