3216 Dibucaine / Official Monographs USP 36

Assay preparation—Transfer an accurately measured vol- ide represented by the difference is equivalent to 129.8 mg ume of Injection, equivalent to about 50 mg of dibucaine, of C15H18Cl6N2O5. to a 100-mL volumetric flask. Dilute with methanol to vol- Assay procedure 2—Transfer about 400 mg of Dichloral- ume, and mix. Where the Injection is labeled to contain phenazone, accurately weighed, to a 125-mL conical flask, 1 mg or less of dibucaine hydrochloride per mL, transfer an add 20 mL of a 1 in 10 solution of sodium acetate, and accurately measured volume of Injection, equivalent to swirl to dissolve. Add 25.0 mL of 0.1 N iodine VS, and allow about 13 mg of dibucaine hydrochloride, to a 50-mL volu- to stand in the dark for 20 minutes, gently swirling occa- metric flask, dilute with methanol to volume, and mix. Pass sionally. Add 10 mL of chloroform, rinsing the walls of the through a suitable filter having a 0.5-µm or finer porosity. flask, and swirl until the precipitate is dissolved. Titrate the Procedure—Separately inject equal volumes (about 10 µL, excess iodine with 0.1 N sodium thiosulfate VS, adding or 20 µL where the concentration of dibucaine hydrochlo- 3 mL of starch TS as the endpoint is approached. Perform a ride is about 0.25 mg per mL) of the Standard preparation blank titration (see Residual Titrations under Titrimetry 〈541〉). and the Assay preparation into the chromatograph, record The difference between the titrations represents the amount the chromatograms, and measure the area responses for the of iodine consumed. Each mL of 0.1 N iodine consumed is major peaks. Calculate the quantity, in mg, of dibucaine equivalent to 25.95 mg of C15H18Cl6N2O5. hydrochloride (C20H29N3O2 · HCl) in each mL of the Injection Calculation—The difference between the percentages cal- taken by the formula: culated from Assay procedure 1 and Assay procedure 2 is not more than 1.5%. C(v / V)(rU / rS) in which C is the concentration, in mg per mL, of USP Dibu- caine Hydrochloride RS in the Standard preparation; v is the volume, in mL, of the Assay preparation; V is the volume, in . mL, of Injection taken; and rU and rS are the area responses Dichlorphenamide of the dibucaine peaks obtained from the Assay preparation and the Standard preparation, respectively.

. Dichloralphenazone C6H6Cl2N2O4S2 305.16 1,3-Benzenedisulfonamide, 4,5-dichloro-. 4,5-Dichloro-m-benzenedisulfonamide [120-97-8]. » Dichlorphenamide contains not less than 98.0 percent and not more than 101.0 percent of C6H6Cl2N2O4S2, calculated on the dried basis. C15H18Cl6N2O5 519.03 1,2-Dihydro-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one, Packaging and storage—Preserve in well-closed contain- compound with 2,2,2-trichloro-1,1-ethanediol (1:2). ers. Antipyrine, compound with chloral hydrate (1:2) USP Reference standards 〈11〉— [480-30-8]. USP Dichlorphenamide RS » Dichloralphenazone contains not less than Identification— A: To 10 mL of a 1 in 10,000 solution in sodium hydrox- 97.0 percent and not more than 100.5 percent of ide solution (1 in 2500) add 0.1 mL of hydrochloric acid: it C15H18Cl6N2O5, determined by both Assay exhibits absorption maxima at 295 ± 2 nm and at 286 ± 2 procedures. nm. The ratio A295 / A286 is between 0.90 and 1.00. B: Infrared Absorption 〈197M〉. Packaging and storage—Preserve in well-closed contain- ers. Melting range 〈741〉: between 236.5° and 240°. USP Reference standards 〈11〉— Loss on drying 〈731〉—Dry it at a pressure not exceeding USP Dichloralphenazone RS 5 mm of mercury at 100° to constant weight: it loses not more than 1.0% of its weight. Identification— Residue on ignition 〈281〉: not more than 0.2%. A: Infrared Absorption 〈197K〉. Chloride 〈221〉—To 100 mg add 25 mL of 8 N nitric acid, B: Dissolve 0.1 g of it in 10 mL of water containing 0.1 g and warm on a steam bath to dissolve. Cool to room tem- of sodium nitrite, and add 1 mL of 2 N sulfuric acid: a green perature: the solution shows no more chloride than corre- color is produced. sponds to 0.28 mL of 0.020 N hydrochloric acid (0.20%). Residue on ignition 〈281〉: not more than 0.1%. Selenium 〈291〉: 0.003%, a 100-mg test specimen, mixed Heavy metals, Method II 〈231〉: 0.001%. with 100 mg of magnesium oxide, being used. Assay—Perform the following determinations. Heavy metals, Method II 〈231〉: 0.001%. Assay procedure 1—Transfer about 1500 mg of Dichloral- Assay— phenazone, accurately weighed, to a beaker, add 10 mL of Mobile solvent—Prepare a suitable solution of 0.02 M water and 20.0 mL of 0.5 N sodium hydroxide VS. Allow to monobasic sodium phosphate and 0.02 M dibasic sodium stand for 2 minutes, and titrate with 0.5 N sulfuric acid VS phosphate in acetonitrile and water (approximately 1:1) to a colorless phenolphthalein endpoint. Titrate this neutral- such that the retention time of Dichlorphenamide is approx- ized solution with 0.1 N silver nitrate VS, using potassium imately 6 minutes. chromate TS as the indicator. To the volume of 0.5 N sulfu- ric acid used in the first titration add four-fifteenths of the Standard preparation—Dissolve an accurately weighed volume of 0.1 N silver nitrate used in the second titration, quantity of USP Dichlorphenamide RS in Mobile solvent to and subtract the sum obtained from the volume of 0.5 N obtain a solution containing about 1 mg per mL. sodium hydroxide added. Each mL of 0.5 N sodium hydrox-