Identification
Transfer a quantity of Ophthalmic Ointment, equivalent to about 5 mg of erythromycin, to a separator containing 50 mL of solvent hexane. Shake until dissolved. Extract with three separate 20-mL portions of methanol. Combine the methanol extracts in a beaker, and evaporate to dryness. Dissolve the residue in 2 mL of methanol (test solution). Proceed as directed in the
Identification test under
Erythromycin Delayed-Release Capsules, beginning with Prepare a Standard solution of
USP Erythromycin RS.