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

• Published in: Journal of infrared, millimeter and terahertz waves Vol. 37; no. 5; pp. 486 - 497
• Main Authors: Baek, Seung Hyun, Kang, Ju Hee, Hwang, Yeun Hee, Ok, Kang Min, Kwak, Kyungwon, Chun, Hyang Sook
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2016; Springer Nature B.V
• Subjects: Absorption; Classical Electrodynamics; Density functional theory; Electrical Engineering; Electronics and Microelectronics; Engineering; Feasibility studies; Food; Frequency ranges; Insecticides; Instrumentation; Molecular interactions; Regression analysis; Regression coefficients; Solid state; Spectrum analysis; Time domain analysis; Wheat; Methomyl; Wheat and rice flours; Detection; Solid-state density functional theory; Terahertz time-domain spectroscopy
• ISSN: 1866-6892; 1866-6906
• DOI: 10.1007/s10762-015-0234-9

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.