Chromatographic purity—
[NOTE—The
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%.
Assay—
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 C
8H
8Cl
3N
3O
4S
2 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.
;)
for 4 hours: it loses not more than 0.5% of its weight.