(dye'' klor fen' a mide).
» Dichlorphenamide contains not less than 98.0 percent and not more than 101.0 percent of C6H6Cl2N2O4S2, calculated on the dried basis.
Packaging and storage Preserve in well-closed containers.
USP Reference standards 11
USP Dichlorphenamide RS
A: To 10 mL of a 1 in 10,000 solution in sodium hydroxide solution (1 in 2500) add 0.1 mL of hydrochloric acid: it exhibits absorption maxima at 295 ± 2 nm and at 286 ± 2 nm. The ratio A295 / A286 is between 0.90 and 1.00.
Melting range 741: between 236.5 and 240.
Loss on drying 731 Dry it at a pressure not exceeding 5 mm of mercury at 100 to constant weight: it loses not more than 1.0% of its weight.
Residue on ignition 281: not more than 0.2%.
Chloride 221 To 100 mg add 25 mL of 8 N nitric acid, and warm on a steam bath to dissolve. Cool to room temperature: the solution shows no more chloride than corresponds to 0.28 mL of 0.020 N hydrochloric acid (0.20%).
Selenium 291: 0.003%, a 100-mg test specimen, mixed with 100 mg of magnesium oxide, being used.
Heavy metals, Method II 231: 0.001%.
Mobile solvent Prepare a suitable solution of 0.02 M monobasic sodium phosphate and 0.02 M dibasic sodium phosphate in acetonitrile and water (approximately 1:1) such that the retention time of Dichlorphenamide is approximately 6 minutes.
Standard preparation Dissolve an accurately weighed quantity of USP Dichlorphenamide RS in Mobile solvent to obtain a solution containing about 1 mg per mL.
Assay preparation Accurately weigh about 50 mg of Dichlorphenamide, and prepare as directed for Standard preparation.
Procedure Introduce separately 20-µL portions of the Assay preparation and the Standard preparation into a high-pressure liquid chromatograph (see Chromatography 621) operated at 25, by means of a suitable microsyringe or sampling valve, adjusting the operating parameters such that the peak obtained with the Standard preparation is full-scale. Typically, the apparatus is fitted with a 4-mm × 30-cm column, packed with packing L1, is equipped with an UV detector capable of monitoring absorption at 280 nm and a suitable recorder, and is capable of operating at a column pressure of up to 3500 psi. Five replicate injections of the Standard preparation show a relative standard deviation of not more than 1.5%. Calculate the quantity, in mg, of C6H6Cl2N2O4S2 in the portion of Dichlorphenamide taken by the formula:
50C(AU / AS)in which C is the concentration, in mg per mL, of USP Dichlorphenamide RS in the Standard preparation; and AU and AS are the area responses obtained at equivalent retention times from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2877Pharmacopeial Forum: Volume No. 29(4) Page 1025