Overlapping of Second Order Scattering and Frequency Double Scattering Spectra Method and Resonance Rayleigh Scattering Method for the Determination of 6-Benzyladenine in Bean Sprout

In this work, second order scattering (SOS), frequency double scattering (FDS), the overlapping method of the two (SFOM), and resonance Rayleigh scattering (RRS) method had been developed for sensitive determination of trace 6-benzyladenine (BA) in bean sprout samples. In pH 1.6 HCl-NaAc medium, Pd(II) reacted with BA to form a 1:1 chelate complex, and then, the complex further self-aggregated into nanoparticles Pd(II)-BA]_n. This resulted in a remarkable enhancement of resonance Rayleigh-scattering (RRS), second-order scattering (SOS), and frequency-double scattering (FDS) spectra. The maximum wavelengths were located at 312 nm (RRS), 632 nm (SOS), and 323 nm (FDS), respectively. The increments of scattering intensities ΔI were directly proportional to the concentration of BA in certain ranges. The detection limits were 7.0 nmol L^?1 (0.79 μg/kg, RRS), 10.3 nmol L^?1 (1.16 μg/kg, SOS), 39.4 nmol L^?1 (4.44 μg/kg, FDS), and 8.6 nmol L^?1 (0.96 μg/kg, SFOM). In addition, the optimum conditions of the reaction, and the effects of coexisting substances were investigated. The results showed that these methods exhibited a high selectivity. The reaction mechanism and the reasons for the enhancement of scattering were also discussed. Moreover, the feasibility for the SFOM method was illustrated in this paper. The proposed method had been successfully applied to determine a trace amount of BA in bean-sprout samples with the recoveries of 97.0–103.0 %.