Fluorimetric determination of aminoglycoside antibiotics using lanthanide probe ion spectroscopy

The application of probe ion fluorimetry has succeeded in the microdetermination of six aminoglycoside antibiotics: neomycin, streptomycin, gentamicin, tobramycin, amikacin and kanamycin as sulfate salts in pure form and in some pharmaceutical preparations. The method is based on the reaction of Eu(3+) ions with aminoglycosides through amino and hydroxy groups. Such interactions enhance the intensity of the 616 nm fluorescence emission of the Eu(3+) ion. The fluorescence at 592 nm comes from a non-hypersensitive transition and is not affected by the ligand which is bound to the probe ions. The intensity ratio R, defined as I (592)I (616) was used to determine the amount of free and bound europium ions. A linear relationship between bound europium ions and aminoglycoside was found within the concentration ranges 20-100 ppm for neomycin, 5-60 ppm for streptomycin, and 10-70 ppm for gentamicin, tobramycin, amikacin, and kanamycin as sulfate salts. The percentage recoveries ranged from 99.22 to 101.07, with standard deviations ranging from +/- 1.5 to +/- 4.38. The relative stability constants ranged from 5 x 10(3) to 2 x 10(4). The optimum reaction conditions were studied and the results obtained compared favourably with the fluorimetric method using fluorescmine reagent.