Identification—
To a quantity of the contents of Capsules, equivalent to about 400 mg of sulfinpyrazone, add 20 mL of a 1 in 20 solution of methanol in dehydrated alcohol, boil, and filter. Add water to the filtrate until the solution becomes turbid, allow to stand until crystals form (1 to 2 hours), remove the crystals by filtration, and dry at 105
for 1 hour: the sulfinpyrazone so obtained melts between 128
and 134
, and responds to the
Identification test under
Sulfinpyrazone.
Dissolution 
711
—
Apparatus 1:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of C
23H
20N
2O
3S dissolved from UV absorbances at the wavelength of maximum absorbance at about 259 nm of filtered portions of the solution under test, suitably diluted with
Dissolution Medium, in comparison with a Standard solution having a known concentration of
USP Sulfinpyrazone RS in the same
Medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C23H20N2O3S is dissolved in 45 minutes.
Assay—
Acetonitrile and tetrahydrofuran mixture—
Prepare a mixture of acetonitrile and tetrahydrofuran (4:1).
Mobile phase—
Prepare a degassed and filtered solution of dilute phosphoric acid (3 in 1000) and Acetonitrile and tetrahydrofuran mixture (65:35).
Internal standard solution—
Prepare a solution of Benzoic Acid in acetonitrile having a concentration of about 2 mg per mL.
Standard preparation—
Transfer about 100 mg, accurately weighed, of
USP Sulfinpyrazone RS to a 200-mL volumetric flask, add 100 mL of acetonitrile, mix, add 10.0 mL of
Internal standard solution, dilute with acetonitrile to volume, and mix. Filter, discarding the first 5 mL of the filtrate.
Assay preparation—
Remove as completely as possible, and weigh, the contents of not less than 20 Capsules, and mix. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of sulfinpyrazone, to a 200-mL volumetric flask, add 100 mL of acetonitrile, mix, add 10.0 mL of Internal standard solution, dilute with acetonitrile to volume, and mix. Filter, discarding the first 5 mL of the filtrate.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 235-nm detector and a 4.6-mm × 10-cm column that contains packing L1. The flow rate is about 3 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed under
Procedure: the relative retention times are about 0.2 for benzoic acid and 1.0 for sulfinpyrazone; the resolution,
R, between benzoic acid and sulfinpyrazone is not less than 13; and the relative standard deviation is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. The resolution,
R, between benzoic acid and sulfinpyrazone is not less than 13. Calculate the quantity, in mg, of C
23H
20N
2O
3S in the portion of Capsule contents taken by the formula:
200C(RU / RS),
in which
C is the concentration, in mg per mL, of
USP Sulfinpyrazone RS in the
Standard preparation, and
RU and
RS are the relative peak response ratios obtained from the
Assay preparation and the
Standard preparation, respectively.
