Resonance Rayleigh scattering measurement of aminoglycoside antibiotics with Evans Blue

In a weak acid medium, some aminoglycoside antibiotics, such as kanamycin (KANA), gentamicin (GEN), tobramycin (TOB) and neomycin (NEO), or acid bisazo dye Evans Blue (EB) can only produce very weak resonance Rayleigh scattering (RRS) signals. However, when two agents react with each other to form ion-association complexes, the RRS intensity can be greatly enhanced and a new RRS spectrum with a significant enhancement of the RRS intensity in the wavelength range from 350 nm to 600 nm can be observed. The maximum scattering peak is at 570 nm. There is a linear relationship between the RRS intensity and the antibiotic concentration in the range of 0.01-6.0 microg mL(-1) at 570 nm. This RRS method for the determination of aminoglycoside antibiotics at trace-amount levels has been developed. The detection limits (3sigma) of the four antibiotics, whose order of sensitivity from high to low ranks as KANA > NEO > TOB > GEN, are 5.2-6.9 ng mL(-1). This method has good selectivity and has been successfully applied to the quick determination of antibiotics not only for injections and ear drops, but for clinic serum samples as well. In addition, the reaction mechanism by using a quantum chemistry method and the influencing factors of the RRS spectra and the enhancement reasons of RRS have been discussed.