Application of THz spectroscopy to pesticide detection

Application possibility of terahertz (THz) spectroscopy to pesticide inspection in agricultural products was investigated. Several pesticides showed specific absorption in the range of 20-400 cm^-1, and a high correlation was obtained between the concentration and the second derivative value of the spectra of cis-Permethrin. The calibration models were evaluated using some parameters such as coefficient of determination (R²), standard error of prediction (SEP), bias between actual and predicted concentration and ratio prediction to deviation (RPD) parameter. Good prediction performances of PLS and MLR were obtained for R² with 0.95 and 0.96 respectively, and for RPD with 3.95 and 5.06 respectively. Next, broad absorption spectra of the vegetables such as tomato, spinach, cabbage and strawberry were observed. When two kinds of material were mixed, absorptions of each material were observed as superposition.