Identification—
The UV absorption spectrum of the Nasal Solution, diluted with water, if necessary, to a concentration of about 1 in 4000, exhibits maxima and minima at the same wavelengths as that of a similar solution of
USP Tetrahydrozoline Hydrochloride RS, concomitantly measured.
Assay—
Oxidized nitroprusside reagent—
Dissolve 1.0 g of sodium nitroferricyanide in water to make 10.0 mL (Solution A). Dissolve 1.0 g of potassium ferricyanide in water to make 10.0 mL (Solution B). Transfer 1.0 mL each of Solution A and Solution B to a 100-mL volumetric flask, add 1 mL of sodium hydroxide solution (1 in 10), and allow to stand until the solution changes to a light yellow color (about 20 to 30 minutes). Dilute with water to volume, and mix. Store in a refrigerator or keep in an ice bath, and use within 4 hours.
Standard preparation—
Dissolve a suitable quantity of
USP Tetrahydrozoline Hydrochloride RS, accurately weighed, in water, and dilute quantitatively with water to obtain a solution having a known concentration of about 100 µg per mL.
Assay preparation—
Transfer an accurately measured volume of Nasal Solution, equivalent to about 10 mg of tetrahydrozoline hydrochloride, to a 100-mL volumetric flask, dilute with water to volume, and mix.
Procedure—
Transfer 5.0 mL each of the
Standard preparation and the
Assay preparation to separate glass-stoppered test tubes. Pipet 5 mL of water into a third tube to provide a blank. To each tube add 4.0 mL of
Oxidized nitroprusside reagent, mix, and allow to stand at 30
for 15 minutes. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 570 nm, with a suitable spectrophotometer, using the blank to set the instrument. Calculate the quantity, in mg, of C
13H
16N
2·HCl in each mL of the Nasal Solution taken by the formula:
0.1(C / V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Tetrahydrozoline 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.
61
—
It meets the requirements of the tests for absence of Staphylococcus aureus and Pseudomonas aeruginosa.