Assay for chloramphenicol—
Standard preparation— Proceed as directed
for Standard preparation in the Assay
under Chloramphenicol Ophthalmic Ointment.
Proceed as directed for Procedure
in the Assay
Calculate the quantity, in mg, of C11
in the portion of Ophthalmic Ointment taken by the formula:
in which the terms are as defined therein.
Assay for polymyxin—
Proceed as directed for
polymyxin under Antibiotics—Microbial
using an accurately weighed portion of Ophthalmic Ointment, equivalent to
about 5000 Polymyxin B Units, shaken in a separator containing about 50 mL
of ether and extracted with four 20-mL portions of Buffer
Combine the aqueous extracts in a 100-mL volumetric flask,
dilute with Buffer No. 6
to volume, and mix.
Dilute an accurately measured portion of this solution quantitatively with
Buffer No. 6
to obtain a Test
having a concentration assumed to be equal to the median
dose level of the Standard.