Identification—
B:
The retention time of the main peak in the chromatogram of the
Assay preparation, obtained as directed in the
Assay, corresponds to that of the main peak observed in the chromatogram of the
Standard preparation, obtained as directed in the
Assay.
Acidity—
Prepare a suspension of 3.0 g of it in 150.0 mL of carbon dioxide-free water, and heat at 70
for 5 minutes, maintaining the suspension. Cool rapidly in an ice bath to 20 ± 0.5
, stirring by mechanical means. Filter the suspension using vacuum, and collect the filtrate. Titrate 25.0 mL of the clear filtrate with 0.1 N sodium hydroxide VS, using 2 drops of thymolphthalein TS as the indicator. Transfer a second 25.0-mL portion of the clear filtrate to a 250-mL conical flask, add 10 mL of hydrochloric acid, and cool in an ice bath to 15
. Add about 25 g of crushed ice, prepared from frozen purified water, and titrate with 0.1
M sodium nitrite VS, stirring vigorously, until the titrated solution produces an immediate, stable, blue color on starch-iodide paper. The volume of 0.1 N sodium hydroxide consumed in the titration of the first 25.0-mL portion of the filtrate does not exceed the volume of 0.1
M sodium nitrite consumed in the titration of the second 25.0-mL portion of the filtrate by more than 0.5 mL.
Assay—
pH 2.5 phosphate buffer—
Dissolve 14 g of monobasic potassium phosphate in 1600 mL of water, adjust with phosphoric acid to a pH of 2.5 ± 0.1, dilute with water to 2000 mL, and mix.
Mobile phase—
Prepare a filtered and degassed mixture of
pH 2.5 phosphate buffer and methanol (700:300). Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
Standard preparation—
Prepare a stock solution of
USP Sulfachlorpyridazine RS in methanol having a known concentration of about 0.5 mg per mL. Transfer 3.0 mL of this stock solution to a 100-mL volumetric flask, dilute with
Mobile phase to volume, and mix. Filter this solution through a nylon filter having a porosity of 0.5 µm or finer, and use the filtrate as the
Standard preparation. The
Standard preparation contains about 15 µg of
USP Sulfachlorpyridazine RS per mL.
Assay preparation—
Transfer about 50 mg of Sulfachlorpyridazine, accurately weighed, to a 100-mL volumetric flask. Dissolve in and dilute with methanol to volume, and mix. Transfer 3.0 mL of this solution to a second 100-mL volumetric flask, dilute with Mobile phase to volume, and mix. Filter this solution through a filter having a porosity of 0.5 µm or finer, and use the filtrate as the Assay preparation.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 265-nm detector, a 4.6-mm × 25-cm analytical column containing 5-µm packing L1, and a guard column containing 5-µm packing L1, and is maintained at about 40
. The flow rate is about 1 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20 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
10H
9ClN
4O
2S in the portion of Sulfachlorpyridazine taken by the formula:
(10 / 3)(C)(rU / rS),
in which
C is the concentration, in µg per mL, of
USP Sulfachlorpyridazine RS in the
Standard preparation; and
rU and
rS are the sulfachlorpyridazine peak area responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
