(klor' sue lon).
» Clorsulon contains not less than 98.0 percent and not more than 101.0 percent of C8H8Cl3N3O4S2, calculated on the dried basis.
Packaging and storage Preserve in well-closed containers.
Labeling Label it to indicate that it is for veterinary use only.
USP Reference standards 11
B: The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for clorsulon, the retention time of which corresponds to that of the Standard preparation obtained as directed in the Assay.
Melting range 741: between 197 and 203.
Loss on drying 731 Dry it in vacuum at 100 for 4 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Heavy metals, Method II 231: 0.003%.
Chromatographic purity [noteThe Standard solutions and Test solutions should be stored in low-actinic glassware. ] Prepare a solution of Clorsulon in methanol containing 10.0 mg per mL (Test solution). Prepare a solution of USP Clorsulon RS in methanol containing 10.0 mg per mL (Standard solution A). Transfer 1.0 mL of Standard solution A to a 100-mL volumetric flask, dilute with methanol to volume, and mix (Standard solution B). Apply 10-µL portions of the Test solution and of Standard solution A, and 5- and 10-µL portions of Standard solution B to 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 chromatograms in a solvent system consisting of a mixture of chloroform and methanol (4:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, allow the solvent to evaporate, and examine the plate under short-wavelength UV light:the chromatograms show principal spots at about the same RF value. Estimate the amounts of any additional spots observed in the chromatogram of the Test solution by comparing them with the spots in the two chromatograms obtained from Standard solution B, corresponding to 0.5% and 1.0% of impurity:no spot, other than the principal spot, in the chromatogram of the Test solution is larger or more intense than that of the principal spot in the chromatogram obtained from the 5-µL portion of Standard solution B (0.5%), and the sum of all such impurities is not more than 2.0%.
Mobile phase Prepare a filtered and degassed mixture of water, acetonitrile, and glacial acetic acid (70:30:0.1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Dissolve an accurately weighed quantity of USP Clorsulon RS in Mobile phase to obtain a solution having a known concentration of about 0.1 mg per mL. Store the solution in low-actinic glassware.
Assay preparation Transfer about 50 mg of Clorsulon, accurately weighed, to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 5.0 mL of this solution to a second 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Store the solution in low-actinic glassware.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 7400 theoretical plates; the tailing factor is not more than 1.4; and the relative standard deviation for replicate injections is not more than 1.0%.
Procedure Separately inject equal volumes (about 30 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C8H8Cl3N3O4S2 in the portion of Clorsulon taken by the formula:
500C(rU / rS)in which C is the concentration, in mg per mL, of USP Clorsulon RS in the Standard preparation; and rU and rS are the clorsulon peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2740Pharmacopeial Forum: Volume No. 28(2) Page 269