» Decoquinate Premix contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C24H35NO5, the labeled amount being between 1 g and 10 g per 100 g of Premix.
Packaging and storage Preserve in well-closed containers.
Labeling Label it to indicate that it is for veterinary use only.
Identification To an accurately weighed quantity of it, equivalent to about 100 mg of decoquinate, add 40 mL of chloroform, and heat under a reflux condenser on a water bath for 20 minutes, cool, and filter. Use the filtrate as the test solution. Apply 10-µL portions of the test solution and of a Standard solution in chloroform containing 2.5 mg of USP Decoquinate RS per mL to the starting line of a suitable thin-layer chromatographic plate (see Chromatography 621) 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 UV light: the RF value 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 200 mg of decoquinate, with 50 mL of chloroform in a small continuous extraction apparatus for 8 reflux cycles. Transfer the extract to a 100-mL volumetric flask with the aid of chloroform, cool, dilute with chloroform to volume, and mix. Transfer 5.0 mL of this solution to a second 100-mL volumetric flask, dilute with dehydrated alcohol to volume, and mix. Transfer 5.0 mL of this solution to a third 100-mL volumetric flask, add 10 mL of 0.1 N hydrochloric acid, dilute with dehydrated alcohol to volume, and mix (Assay preparation). Transfer 50 mg of USP Decoquinate RS, accurately weighed, to a 100-mL volumetric flask, add 10 mL of hot chloroform, swirl to dissolve, and while still warm slowly add 70 mL of dehydrated alcohol. Allow to cool, dilute with dehydrated alcohol to volume, and mix. Immediately transfer 10.0 mL of this solution to a second 100-mL volumetric flask, dilute with dehydrated alcohol to volume, and mix. Transfer 10.0 mL of this solution to a third 100-mL volumetric flask, add 10 mL of 0.1 N hydrochloric acid, dilute with dehydrated alcohol to volume, and mix. This Standard preparation contains about 0.005 mg of USP Decoquinate RS per mL. Concomitantly determine the absorbances of the Standard preparation and the Assay preparation at the wavelength of maximum absorbance at about 265 nm, with a spectrophotometer, using a mixture of dehydrated alcohol, 0.1 N hydrochloric acid, and chloroform (90:10:0.25) as the blank. Calculate the percentage of C24H35NO5 in the portion of Premix taken by the formula:
4000(C / W)(AU / AS)in which C is the concentration, in mg per mL, of USP Decoquinate RS in the Standard preparation; W is the quantity, in g, of Premix taken to prepare the Assay preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.
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USP32NF27 Page 2062