Resonance Rayleigh scattering, frequency doubling scattering and absorption spectrum of the interaction for mebendazole with 12-tungstophosphoric acid and its analytical applications

The interaction of mebendazole (MBZ) with12-tungstophosphoric acid (TP) has been investigated by using resonance Rayleigh scattering (RRS) and frequency doubling scattering (FDS) combining with absorption spectrum. In pH 1.0 HCl medium, MBZ reacted with TP to form 3:1 ion–association complex. As a result, not only the spectrum of absorption was changed, but also the intensities of RRS and FDS were enhanced greatly. The maximum RRS, FDS and absorption wavelengths are located at 372, 392 and 260   nm, respectively. The increments of scattering intensity (Δ I ) and absorption (Δ A ) are directly proportional to the concentrations of MBZ in certain ranges. The detection limits (3 σ ) of RRS, FDS and absorption are 0.56, 0.86 and 130.16   ng/mL, respectively. The sensitivity of RRS method is higher than FDS and absorption methods. The optimum conditions of RRS method and the influence factors were discussed in the paper, in addition, the structure of ion–association complex and the reaction mechanism were investigated. Based on the ion–association reaction and its spectral response, the rapid, simple and sensitive RRS method for the determination of MBZ has been developed.