Identification—
B:
Ultraviolet Absorption 
197U
—
Solution:
1 in 100,000.
Medium:
alcohol.
Absorptivities, calculated on the dried basis, at 272 nm do not differ by more than 3.0%.
C:
To about 100 mg, add 3 mL of 2.5 N sodium hydroxide and 50 mL of water, mix until dissolved, and dilute with water to 100 mL. To about 5 mL of this solution, add 100 mg of phenol, and heat to boiling. Cool the solution, and add 0.5 mL of
sodium hypochlorite TS and 3 drops of 2.5 N sodium hydroxide: a yellow color is produced.
D:
To about 10 mg dissolved in 2 mL of diluted hydrochloric acid, add 3 drops of sodium nitrite solution (1 in 100), and dilute with water to 4 mL: the solution turns yellow. Add 1 mL of 2.5 N sodium hydroxide containing 10 mg of 2-naphthol: a red-orange precipitate is formed.
Assay—
Mobile phase—
Dissolve 6 g of monobasic sodium phosphate in water to make 1000 mL. Adjust with 50% (w/v) sodium hydroxide solution to a pH of 7.0. Prepare a mixture of this solution and methanol (300:100). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Quantitatively dissolve an accurately weighed quantity of
USP Sulfadimethoxine RS in
Mobile phase to obtain a solution having a known concentration of about 0.2 mg per mL. Protect this solution from light.
Assay preparation—
Transfer about 20 mg of Sulfadimethoxine, accurately weighed, to a 100-mL volumetric flask, add about 75 mL of Mobile phase, and swirl to dissolve. Dilute this solution with Mobile phase to volume, and mix. Protect this solution from light.
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 L1. The flow rate is about 1 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the tailing factor is not more than 1.5; and the relative standard deviation for replicate injections is not more than 1.0%.
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. Calculate the quantity, in mg, of C
12H
14N
4O
4S in the portion of Sulfadimethoxine taken by the formula:
100C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Sulfadimethoxine RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
for 3 hours: it loses not more than 0.5% of its weight.