Sensitization of surfactant on the fluorescent reactions of metals

The effects of different surfactants on the Hf-quercetin, Zr-quercetin, Sn-morin, Mg-oxine-5-sulfonic acid (H₂QS), Zn-H₂QS, Cd-H₂QS and Tb-EDTA-sulfosalicylic acid (SSA) systems were investigated. It was found that the fluorescence intensity of each complex studied is greatly increased in the presence of a suitable surfactant. The optimum conditions for the formation of the ternary complexes involving a surfactant were found, and the compositions of these ternary complexes were established by fluorometry. In the presence or absence of a surfactant, the quantum efficiencies (ϕ) of fluorescent complexes were measured by the relative method, and their molar absorptivities at the excitation wavelength (ϵ_ex) were calculated. It was found that the quantum efficiencies and molar absorptivities of fluorescent complexes were increased to various degrees because of the formation of the ionic associated complexes with fixed compositions, thus leading to greatly increased fluorescence intensity. The function of surfactant micelles and the relation between the molecular structures of surfactants and their effects on the fluorescent reactions were discussed. It is noted that only those surfactants with their aromatic system uncharged or unconnected directly with a charged functional group can sensitize the fluorescent reactions. By making use of the surfactant sensitization it is possible to develop some highly sensitive fluorometries of the metals.