» Crotamiton is a mixture of cis and trans isomers containing not less than 97.0 percent and not more than 103.0 percent of C13H17NO.
Packaging and storage Preserve in tight, light-resistant containers.
Solution: 20 µg per mL.
C: To about 10 mL of a saturated solution in water add a few drops of potassium permanganate TS: a brown color is produced, and a brown precipitate is formed on standing.
Specific gravity 841: between 1.008 and 1.011 at 20.
Refractive index 831: between 1.540 and 1.543 at 20.
Residue on ignition 281: not more than 0.1%.
Bound halogen Place 4 drops in a 3-mm (ID) test tube, and add calcium oxide to a height of 1 cm. Heat the tube in a flame, starting from the top, until the reaction is complete, then ignite for a short time. Transfer the contents to a beaker containing 10 mL of water, acidify with nitric acid, and filter. To the filtrate add 0.2 mL of silver nitrate solution (1 in 60): any opalescence obtained is not more than that obtained from a blank solution treated in the same manner.
Assay Transfer about 50 mg of Crotamiton, accurately weighed, to a 100-mL volumetric flask, add cyclohexane to volume, and mix. Transfer 10.0 mL of this solution to a 250-mL volumetric flask, dilute with cyclohexane to volume, and mix. Determine the absorbance of this solution and of a solution of USP Crotamiton RS in the same medium having a known concentration of about 20 µg per mL in 1-cm cells at the wavelength of maximum absorbance at about 242 nm, with a suitable spectrophotometer, using cyclohexane as the blank. Calculate the quantity, in mg, of C13H17NO in the Crotamiton taken by the formula:
2.5C(AU / AS)in which C is the concentration, in µg per mL, of USP Crotamiton RS in the Standard solution; and AU and AS are the absorbances of the assay solution and the Standard solution, respectively.
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USP32NF27 Page 2032