Packaging and storage— Preserve in well-closed containers.

Labeling— Label it to indicate that it is for veterinary use only.

USP Reference standards á11ñ— USP Decoquinate RS.

Identification— To an accurately weighed quantity of it,equivalent to about 100mg of decoquinate,add 40mLof chloroform,and heat under a reflux condenser on a water bath for 20minutes,cool,and filter.Use the filtrate as the test solution.Apply 10-µLportions of the test solution and of a Standard solution in chloroform containing 2.5mg of USP Decoquinate RSper mLto the starting line of a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of chloroform and alcohol (70:30)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,and allow to dry in a current of air.Locate the spots under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

Assay— Extract an accurately weighed quantity of Premix,equivalent to about 200mg of decoquinate,with 50mLof chloroform in a small continuous extraction apparatus for 8reflux cycles.Transfer the extract to a 100-mLvolumetric flask with the aid of chloroform,cool,dilute with chloroform to volume,and mix.Transfer 5.0mLof this solution to a second 100-mLvolumetric flask,dilute with dehydrated alcohol to volume,and mix.Transfer 5.0mLof this solution to a third 100-mLvolumetric flask,add 10mLof 0.1Nhydrochloric acid,dilute with dehydrated alcohol to volume,and mix (Assay preparation).Transfer 50mg of USP Decoquinate RS,accurately weighed,to a 100-mLvolumetric flask,add 10mLof hot chloroform,swirl to dissolve,and while still warm slowly add 70mLof dehydrated alcohol.Allow to cool,dilute with dehydrated alcohol to volume,and mix.Immediately transfer 10.0mLof this solution to a second 100-mLvolumetric flask,dilute with dehydrated alcohol to volume,and mix.Transfer 10.0mLof this solution to a third 100-mLvolumetric flask,add 10mLof 0.1Nhydrochloric acid,dilute with dehydrated alcohol to volume,and mix.This Standard preparationcontains about 0.005mg of USP Decoquinate RSper mL.Concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the wavelength of maximum absorbance at about 265nm,with a spectrophotometer,using a mixture of dehydrated alcohol,0.1Nhydrochloric acid,and chloroform (90:10:0.25)as the blank.Calculate the percentage of C24H35NO5in the portion of Premix taken by the formula: in which Cis the concentration,in mg per mL,of USP Decoquinate RSin the Standard preparation;Wis the quantity,in g,of Premix taken to prepare the Assay preparation;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 574

Phone Number:1-301-816-8178