A: Shake a quantity of Soluble Powder with methanol to obtain a solution containing about 1mg of oxytetracycline hydrochloride per mL.Filter if necessary to obtain a clear solution.Using the filtrate as the Test solution,proceed as directed for Method IIunder Identification—Tetracyclines á193ñ.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Tetrabutylammonium hydrogen sulfate solution,Edetate disodium solution,pH7.5Phosphate buffer,Mobile phase,Standard preparation,System suitability solution,and Chromatographic system— Proceed as directed in the Assayunder Oxytetracycline.

Assay preparation— Transfer an accurately weighed portion of the Soluble Powder,equivalent to about 100mg of oxytetracycline hydrochloride,to a 500-mLvolumetric flask,dilute with 0.01Nhydrochloric acid to volume,and mix.Pass a portion of this solution through a filter having a 0.5-µm or finer porosity.Use the filtrate as the Assay preparation.

Procedure— Proceed as directed for Procedurein the Assayunder Oxytetracycline.Calculate the quantity,in g,of oxytetracycline hydrochloride (C22H24N2O9·HCl)in each g of Soluble Powder taken by the formula: in which 496.90and 460.44are the molecular weights of oxytetracycline hydrochloride and oxytetracycline,respectively;Cis the concentration,in mg per mL,of USP Oxytetracycline RSin the Standard preparation;Pis the assigned potency,in µg of oxytetracycline per mg,of USP Oxytetracycline RS;Wis the weight,in g,of Soluble Powder taken to prepare the Assay preparation;and rUand rSare the oxytetracycline peak responses obtained from the Assay preparationand the Standard preparation,respectively.