Standard solution— Dissolve an accurately weighed quantity of USP Xylometazoline Hydrochloride RS in water to obtain a solution having a known concentration of about 1 mg per mL, and proceed as directed for Test solution.

Test solution— Transfer 10 mL to a suitable separator, add 2 mL of sodium carbonate solution (1 in 10), and extract with 10 mL of chloroform, filtering the extract through anhydrous sodium sulfate. Evaporate the chloroform extract on a steam bath to dryness, and dissolve the residue in 1 mL of a mixture of chloroform and methanol (1:1).

Procedure— Apply separately 5-µL portions of the Test solution and the Standard solution to a suitable thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture (see Chromatography 621). Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform, methanol, and isopropylamine (92:3:3). Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Spray the plate with p-nitrobenzenediazonium tetrafluoroborate solution, prepared by adding 250 mg to 5 mL of water, mixing, and filtering. Spray the plate with sodium carbonate solution (1 in 10): the RF value of the principal spot obtained from the Test solution corresponds to that obtained from the Standard solution.

(Official January 1, 2007)

Standard preparation— Dissolve an accurately weighed quantity of USP Xylometazoline Hydrochloride RS in water to obtain a solution having a known concentration of about 0.5 mg per mL. Transfer 10.0 mL of this solution to a 125-mL separator, and proceed as directed under Assay preparation, beginning with “add 10 mL each of water and dilute hydrochloric acid (1 in 6), respectively.” The concentration of USP Xylometazoline Hydrochloride RS in the Standard preparation is about 100 µg per mL.

Assay preparation— Transfer an accurately measured volume of Nasal Solution, equivalent to about 5 mg of xylometazoline hydrochloride, to a 125-mL separator, add 10 mL each of water and dilute hydrochloric acid (1 in 6), respectively, and extract with three 10-mL portions of methylene chloride. Discard the methylene chloride extracts, add 10 mL of sodium hydroxide solution (1 in 5) to the separator, and extract with three 15-mL portions of methylene chloride. Filter the combined extracts through glass wool into a 50-mL volumetric flask, dilute with methylene chloride to volume, and mix.

Procedure— Transfer 5.0 mL each of the Standard preparation and the Assay preparation, respectively, to separate 10-mL volumetric flasks, and evaporate in a water bath maintained at 40, with the aid of a stream of nitrogen, to dryness. Dissolve the residue in each flask in 0.50 mL of dehydrated alcohol, and add 0.50 mL of dehydrated alcohol to a third 10-mL volumetric flask to provide the blank. To each flask add 0.50 mL of sodium hydroxide solution (1 in 25), swirl, to each add 5.0 mL of sodium nitroferricyanide solution (1 in 200), and mix. After 10 minutes, accurately timed, add 1.0 mL of a saturated solution of sodium bicarbonate to each flask, swirl, and allow to stand for 10 minutes. Dilute each with water to volume, mix, and allow to stand for 15 minutes. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 565 nm, with a suitable spectrophotometer, using the blank to set the instrument. Calculate the quantity, in mg, of xylometazoline hydrochloride (C16H24N2·HCl) in each mL of the Nasal Solution taken by the formula: in which C is the concentration, in µg per mL, of USP Xylometazoline Hydrochloride RS in the Standard preparation, V is the volume, in mL, of Nasal Solution taken, and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.