Diethyltoluamide Topical Solution
» Diethyltoluamide Topical Solution is a solution of Diethyltoluamide in Alcohol or Isopropyl Alcohol. It contains not less than 92.0 percent and not more than 108.0 percent of the labeled amount of the meta-isomer of C12H17NO.
If it contains Alcohol, not less than 95.0 percent and not more than 105.0 percent of the labeled amount of C2H5OH is present.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
Alcohol content (if present) 611: between 29.0% and 89.0% of C2H5OH.
Assay Transfer an accurately weighed quantity of Topical Solution, equivalent to about 200 mg of diethyltoluamide, to a beaker. Place the beaker in a vacuum oven containing silica gel and calcium chloride, and adjusted to a pressure of about 380 mm of mercury, and heat at 35 for 6 hours. Transfer the residue with the aid of carbon disulfide to a 10-mL volumetric flask, and carbon disulfide to volume, and mix. Transfer to a 10-mL volumetric flask about 200 mg of USP Diethyltoluamide RS, accurately weighed, add carbon disulfide to volume, and mix, to obtain the Standard solution. Concomitantly determine the absorbances of both solutions in 1-mm cells at the wavelength of maximum absorbance at about 14.1 µm and at the wavelength of minimum absorbance at about 14.4 µm, with a suitable IR spectrophotometer, using carbon disulfide as the blank. Calculate the quantity, in mg, of the meta-isomer of diethyltoluamide (C12H17NO) in the portion of Topical Solution taken by the formula:
10C(AU14.1 AU14.4) / (AS14.1 AS14.4)in which C is the concentration, in mg per mL, of USP Diethyltoluamide RS in the Standard solution, and AU and AS are the absorbances of the solution from Diethyltoluamide Solution and the Standard solution, respectively, at the wavelengths indicated by the subscripts.
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USP35NF30 Page 2897