Research on thiamethoxam detection and ultraviolet degradation modeling based on fluorescence analysis

The detection and degradation of thiamethoxam by fluorescence spectrometry were researched in this paper. Firstly, the fluorescence spectrum of thiamethoxam was measured and analyzed by LS55 fluorescence spectrometer, and there was a distinct fluorescence peak at 345nm under the excitation of 200 nm. The concentration prediction model was established by using the least square fitting method. Secondly, the fluorescence spectrum of mixed solution between thiamethoxam and apple juice was studied, the prediction model function of thiamethoxam concentration in apple juice was also established, and the correlation coefficient was more than 0.99 which represented a linear relationship between thiamethoxam concentration and fluorescence intensity at 345nm. At last, the thiamethoxam degradation experiment was carried out based on ultraviolet. The degradation model function was established between the time of ultraviolet irradiation and the fluorescence intensity of the characteristic peak, and the degradation rate corresponding to different degradation time was calculated. The results showed that the degradation rate increased with the prolonging of ultraviolet irradiation time. The degradation rate was 35.57% after ultraviolet irradiation for 10 min and it can reach 97.39% after 32 min. The results have a reference value for the detection and degradation of thiamethoxam residues by fluorescence spectrometry.