A sensitive assay of erythrosine using enhanced resonance scattering signals with Fe(phen)32+ in aqueous ethanol media

In a weak acidic Britton–Robinson buffer medium, erythrosine (Ery) can react with Fe(phen)32+ to form 2:1 ion-association complex in the presence of ethanol, which will cause the remarkable enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS), and frequency doubling scattering (FDS) spectra, and the appearance of new spectra of RRS, SOS, and FDS. The maximum wavelengths (λex/λem) of the ion-association complex are located at 350 nm/350 nm for RRS, 280 nm/560 nm for SOS, and 780 nm/390 nm for FDS, respectively. The increments of scattering intensities (ΔI) are directly proportional to the concentration of Ery in a certain range. The detection limits for Ery are 5.6 ng mL−1 for RRS method, 13 ng mL−1 for SOS method, and 17 ng mL−1 for FDS method, respectively. Based on the above researches, a new highly sensitive and simple method for the determination of Ery has been developed. In this work, the spectral characteristics of RRS, SOS, and FDS spectra, the optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism was discussed.