Effects of the interaction between Na2Wo4‐6‐benzylaminopurine anionic chelate and rhodamine 6G on the resonance Rayleigh scattering and fluorescence spectra and their analytical applications

In pH 4.99‐6.06 Britton‐Robinson (BR) buffer medium, 6‐benzylaminopurine (6‐BA) reacted with Na₂WO₄ to form 1:1 anionic chelate (6‐BA·WO₄)^2‐, which further reacted with rhodamine 6G to form ternary ion complexes at room temperature. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) with a maximum RRS wavelength of 316 nm. Meanwhile, the fluorescence of the solution was quenched and excitation (λ_ex) and emission (λ_em) wavelengths of the fluorescence were 290 and 559 nm, respectively. Intensities of RRS enhancing (ΔI_RRS) and fluorescence quenching (ΔI_F) were directly proportional to concentrations of 6‐BA. As a result, RRS and fluorescence quenching for determination of trace amounts of 6‐BA were developed. Under optimal conditions, linear ranges and detection limits of the two methods were 0.05‐15.00 µg/mL and 8.2 ng/mL (RRS), 0.50‐15.00 µg/mL and 17.0 ng/mL, respectively. It was found that the RRS method was superior to fluorescence quenching. The influence of these methods were investigated and results showed that RRS had good selectivity. RRS was applied to determine 6‐BA in vegetable samples with satisfactory results. Furthermore, the reaction mechanisms of the ternary ion‐association system are discussed. In addition, the polarization experiment revealed that the resonance light scattering (RLS) peak of Na₂WO₄‐6‐BA‐R6G consisted mainly of depolarized resonance fluorescence and resonance scattering. It was speculated that light emission fluorescence energy (E_L) transformed into resonance light scattering energy (E_RLS), which was a key reason for enhancement of RRS. Copyright © 2012 John Wiley & Sons, Ltd.