Study On Pesticide Detection Based On Terahertz Frequency Domain Spectroscopy

In recent years,pesticides have been used widely in order to improve the quality and output of crops.However,the use of non-standard pesticides will lead to excessive pesticide residues in crops and the environment.Pesticide residues in agricultural products have become a huge health risk,how to accurately detect pesticide residues has become a concern.Traditional pesticide detection methods have the disadvantages of complex sample preparation,cumbersome operation,and long time-consuming.Terahertz spectroscopy has great application potential in the field of pesticide detection because of its advantages such as high permeability,low energy and obvious fingerprint spectrum.Different from traditional pesticide residue detection,in this paper,we use the terahertz frequency domain spectroscopy to qualitatively identify and quantitatively analyze imidacloprid,acetamiprid and triadimefon in different matrix.The main work of this paper as follows:1.Research on pesticide identification based on terahertz characteristic peaks.The absorption spectra of imidacloprid,acetamiprid and triadimefon within 0.4-1.7THz were obtained,and it was found that the three pesticides had their unique characteristic absorption peaks.The theoretical vibrational frequencies of pesticide molecules were obtained by using the density functional theory,and the source of the characteristic absorption peaks of the three pesticides were explained.2.Detection of pesticide content in solid matrix.The absorption spectra of pesticides with different concentrations were collected by terahertz frequency domain spectroscopy,and the pesticides in food and soil matrices were quantitatively analyzed using chemometric methods such as partial least squares modeling,principal component analysis,and simple linear regression,so as to predict pesticide residues.The absorption spectra of multiple pesticides in soil matrices were calculated based on the least squares model theory,which verified the accuracy of the experimental data.3.Detection of pesticide content in aqueous solution.The absorption spectra of different concentrations of pesticides in aqueous solution were obtained by using a liquid micro cell as a container for pesticide liquid samples.The multiple linear regression model was used to predict the pesticide content in the aqueous solution,and the results showed that the judgment coefficients of the models were all higher than 0.98.It was confirmed that terahertz frequency domain spectroscopy combined with chemometric can be used to detect pesticide content in aqueous solutions.