Resonance Rayleigh scattering spectra of Cu2+-adenine-WO42- system and its analytical application

In pH 6.6-7.2 Tr.is-HCl buffer, Cu2+ could react with adenine (A) to form a 1 : 1 coordination cation [CuA](2+), which only resulted in minor change of the absorption spectrum. However, when this cation further combined with WO42- to form a 1 : 1 ternary ion-association complex [CuA]WO4, the absorption spectrum changed a lot, and the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) enhanced significantly. The maximum wavelengths of RRS, SOS and FDS were located at 310, 592 and 395 nm, respectively. The enhanced intensities of the three methods were proportional to the concentration of adenine in certain ranges, and the detection limit of the most sensitive RRS method was 7.4 x 10(-9) mol L-1 (1.0 ng mL(-1)), indicating that this method could detect trace adenine. In this work, the optimum reaction conditions and the influencing factors have been studied, some potential interferences and the composition of the ion-association complex have been investigated. Meanwhile, the construction of the product and the reaction mechanism have been investigated by atomic force microscopy, transmission electron microscope and quantum chemical calculation. Accordingly, a novel RRS method for determination of adenine has been proposed and applied to detect adenine in real samples with satisfactory results.