Identification—
Vigorously shake by mechanical means a quantity of Ophthalmic Ointment, equivalent to about 3 mg of tobramycin, with 2 mL of chloroform. Add 1 mL of water, shake vigorously by mechanical means for 1 minute, and centrifuge for 15 minutes: the clear upper, aqueous layer so obtained meets the requirements of
Identification test
A under
Tobramycin.
Assay—
Mobile phase, 2,4-Dinitrofluorobenzene reagent, Tris(hydroxymethyl)aminomethane reagent, Standard preparation, Resolution solution, and Chromatographic system—
Proceed as directed in the Assay under Tobramycin.
Assay preparation—
Transfer an accurately weighed portion of Ophthalmic Ointment, equivalent to about 4.5 mg of tobramycin, to a separator, add 50 mL of ether, and extract with four 20- to 25-mL portions of water. Combine the water extracts in a 100-mL volumetric flask, dilute with water to volume, and mix.
Derivatization procedure—
Proceed as directed in the
Assay under
Tobramycin, except to use 15.0 mL of
Assay preparation instead of 4.0 mL.
Procedure—
Proceed as directed in the
Assay under
Tobramycin. Calculate the quantity of tobramycin (C
18H
37N
5O
9), in mg, in the portion of Ophthalmic Ointment taken by the formula:
in which the terms are as defined therein.
71
—
It meets the requirements when tested as directed for Membrane Filtration under Test for Sterility of the Product to be Examined..