In acid solution,La（Ⅲ）and water-soluble aniline blue（ABWS）reacted with gentamycin sulfate（GEN）and tobramycin sulfate（TOB）respeetively,to form ternary ion association complexes wilh an obvious absorption peak and an fading peak,and cause the fading of ABWS.The maximum positive absorption wavelengths were 672nm,and their molar absorptivities（Ε）were 1.66×104L·mol·cm-1（GEN）and 2.59×104L·mol-1·cm-1（TOB）The maximum negative absorption wavelengths arere 610nm（GEN）and 614nm（TOB）,and their molar absorptivities（ε）arere 4.78×104L·cm-1（GEN）and 7.45×104L·mol-1·cm-1（TOB）;When the dual-wavelength absorption spectrometry was used to determine the concentrations of gentamycin or tobramycin,their molar absorptivities ε can reach 6.44×104L·mol-1·cm-1（GEN）and 1.00×105L·mol-1·cm-1（TOB）.This method was used to determine the content of gentamycin and tobramycin in inject lipuid and in human urine with satisfactory results.
Density Functional Method （DFT） B3LYP was performed to study the isomeration mechanism of HNO2 at the 6-31++G**basis sets and at the same time the potential energy curves were tracked. The geometric configurations of reactants, intermediates, transition states and products were optimized at B3LYP/6-31++G** level and the energies were calculated by using QCISD（T）/6-31++G** method. The results show that the most stabilized geometry structure is trans-HONO（M2） and the secondary stable geometric structure is HNO （O）.For other isomers, HNO（O）、HNOO and HO（O）N, are also characterized with a strong stability. In certain conditions, isomerization between all the isomers can be performed.
