Identification—
Transfer a volume of Ophthalmic Suspension,equivalent to about 50mg of natamycin,to a 200-mLvolumetric flask,and add water to make a volume of 5mL.Proceed as directed in the
Identificationtest under
Natamycin,beginning with “Add 100mLof a 1in 1000solution of glacial acetic acid in methanol:”the specified result is obtained.
Assay—
[NOTE—Throughout the
Assay protect from direct light all solutions containing natamycin.
]
Mobile phase
,
Standard preparation,Resolution solution,and
Chromatographic system—Proceed as directed in the
Assayunder
Natamycin.
Assay preparation—
Transfer an accurately measured volume of Ophthalmic Suspension,equivalent to about 50mg of natamycin,to a 250-mLvolumetric flask.Add 12.5mLof tetrahydrofuran,and sonicate for 10minutes.Add 150mLof methanol,and swirl to dissolve.Add 60mLof water,and mix.Allow to cool to room temperature.Dilute with water to volume,and mix.Filter this solution through a suitable membrane filter of 0.5-µm or finer porosity.
Procedure—
Proceed as directed in the
Assayunder
Natamycin.Calculate the quantity,in mg,of C
33H
47NO
13in each mLof the Ophthalmic Suspension taken by the formula:
0.25C(PS/V)(rU/rS),
in which
Cis the concentration,in mg per mL,of
USP Natamycin RSin the
Standard preparation,PSis the stated content,in µg per mg,of
USP Natamycin RS,
Vis the volume,in mL,of Ophthalmic Suspension taken,and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.