A liquid-chromatographic method for the determination of tobramycin

A rapid and sensitive liquid-chromatographic method was developed to quantify the release of tobramycin from polymeric drug delivery systems in vitro. Pre-column derivatization of tobramycin and kanamycin B sulphate (internal standard) was carried out with 2,4,6-trinitrobenzenesulphonic acid. The sample volume required was only 50 microliters. The chromatographic separation was achieved on an octyl reversed-phase column with UV detection at 340 nm. This isocratic method was performed at ambient temperature and required only 8 min of chromatography time. The standard curves were linear over the concentration range 0.50-50.0 mg l-1. Inter-day and intra-day relative standard deviations ranged from 3.6 to 9.3% and from 1.6 to 6.8%, respectively. The assay method was used to determine the tobramycin content in different pharmaceutical formulations and to study the stability of the drug both in the solid-state and in solution.