Detection of Methomyl, a Carbamate Insecticide, in Food Matrices Using Terahertz Time-Domain Spectroscopy

Abstract

The aim of this study was to investigate the feasibility of detecting methomyl, a carbamate insecticide, in food matrices (wheat and rice flours) using terahertz time-domain spectroscopy (THz-TDS). In the frequency range 0.1-3 THz, the characteristic THz absorption peaks of methomyl at room temperature were detected at 1 (33.4 cm −1 ), 1.64 (54.7 cm −1 ), and 1.89 (63.0 cm −1 ) THz. For detailed spectral analysis, the vibrational frequency and intensity of methomyl were calculated using solid-state density functional theory to mimic molecular interactions in the solid state. Qualitatively, the simulated spectrum was in good agreement with the experimental spectrum. Analysis of the individual absorption modes revealed that all of the features in the THz spectrum of methomyl were mainly generated from intermolecular vibrations. The peak appearing at 1 THz (33.4 cm −1 ) was then selected and tested for its suitability as a fingerprint for detecting methomyl in food matrices. Its absorbance was dose-dependently distinguishable from that of wheat and rice flours. The calibration curve of methomyl had a regression coefficient of >0.974 and a detection limit of <3.74 %. Accuracy and precision expressed as recovery and relative standard deviation in interday repeatability were in the ranges 78.0-96.5 and 2.83-4.98 %, respectively. Our results suggest that THz-TDS can be used for the rapid detection of methomyl in foods, but its sensitivity needs to be improved.

Spectral Characterization and Molecular Dynamics Simulation of Pesticides Based on Terahertz Time-Domain Spectra Analyses and Density Functional Theory (DFT) Calculations

“…Pesticides are chemically synthesized compounds of several biological macromolecules, which can be used to control grasses, diseases, harmful insects, and pests that endanger agriculture and forestry [ 18 , 19 ]. In addition, they can also be used to purposefully regulate, control, and affect the metabolism, growth, development, and reproduction of plants [ 20 , 21 ]. However, serious issues of food safety and environmental pollution have attracted more and more attention due to the misuse of these toxic residue pesticides [ 22 , 23 ].…”

THz Spectroscopic Investigation of Wheat-Quality by Using Multi-Source Data Fusion

“…With regards to the qualitative and quantitative analysis of material using THz waves, many researchers have been focusing on the optical and spectral characteristics of the material within the THz band, and they carried out the measurement of the THz absorption coefficient and the refractive index coefficient, as well as an analysis of this single optical parameter. Many studies [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ] have reported the combination of THz spectroscopy and chemometric methods (principal component analysis, partial least squares, support vector machines) to achieve a quantitative analysis of materials, and they achieved good results. The research group [ 23 ] used THz-TDS technology and the chemometric method to identify samples of different quality.…”

Larvicidal activity of synthetic tropane alkaloids against Ascia monuste orseis (Lepidoptera: Pieridae)

“…Compounds such as carbaryl, methomyl, carbofuran and methiocarb are among the carbamate insecticides commercially registered. The natural products cocaine, scopolamine and atropine are examples of tropane alkaloids that exhibit insecticidal activity.…”