Color Reaction of La and Evans Blue with Aminoglycoside Antibiotics and Its Analytical Applications

In the medium of pH 3.5～6.0, La(Ⅲ) and Evans blue(EB) react with aminoglycoside antibio- tics, such as neomycin sulfate(NEO), kanamycin sulfate(KANA), gentamycin sulfate(GEN) and tobramycin sulfate(TOB), to form ternary blue ion association complexes with an obvious absorption peak and an fading peak. The maximum absorption wavelengths are between 668 nm and 674 nm, the linear ranges in 0～1.2×10 -5 g/mL to 0～1.40×10 -5 g/mL, with molar absorptivities(e) between 3.10×10 4 and 6.17× 10 4 L/(mol·cm). The maximum fading wavelengths are in between 614 nm and 620 nm, and the linear ranges in 0～9.0×10 -6 g/mL to 0～1.7×10 -5 g/mL, with molar absorptivities(e) between 4.33×10 4 and 1.04×10 5 L/(mol·cm). Their sensitivity is much higher when the positive minus wavelengths overlapping absorption spectrometry is used to determine the concentrations of aminoglycoside antibiotics. The reaction conditions, the important properties in analytical chemistry and the compound ratio of ternary ion association complexes(La∶EB∶GEN=1∶2∶3) have been discussed. The method has been applied to determining the content of the commerce aminoglycoside antibiotics with satisfactory results.