Resonance Rayleigh scattering method for the determination of aminoglycoside antibiotics with Trypan Blue

In weak acidic medium, some aminoglycoside antibiotics, such as kanamycin (KANA), gentamicin (GEN), tobramycin (TOB), and neomycin (NEO), or acid bisazo dye trypan blue (TB) can only produce very weak resonance Rayleigh scattering (RRS) signals. However, when the two agents react with each other to form the ion association complexes, the RRS intensity can be enhanced greatly and a new RRS spectrum and a significant enhancement of the RRS intensity in the wavelength range 350-600 nm can be observed. The maximum scattering peak was at 580 nm. There is a linear relationship between the RRS intensity and the antibiotic concentration in the range 0.01-6.0 mug mL(-1) at 580 nm. This RRS method has therefore been developed for the determination of trace levels of aminoglycoside antibiotics. The detection limits (3sigma) of the four antibiotics, whose order of sensitivity KANA > NEO > TOB > GEN, are 6.1-8.1 ng mL(-1). This method has a good selectivity and has been successfully applied to the quick determination of antibiotics not only for injections and ear dips, but clinic serum samples as well. In addition, quantum chemistry-based analysis of the reaction mechanism, the factors influencing the RRS spectra, and the reasons for the enhancement of RRS are discussed.