Method for detection of pesticide residue based on terahertz time domain spectroscopy

Terahertz time-domain spectroscopy (THz-TDS) technique is a newly developed promising spectroscopy technique based on ultrafast laser technology. A method for pesticide detection based on THz-TDS was reported. Two pesticides, methomyl and oxyfluorfen, were investigated to prove its feasibility. THz-TDS was used to measure their terahertz time domain signals. And their refractive index and absorption coefficient between 0.2 THz and 2.0 THz were calculated by using models based on Fresnel equations. The experimental results indicate that a series of distinct sharp characteristic absorption peaks can be observed clearly and absorption spectra of these two pesticides are completely different. Our analysis show that these absorption peaks may originate from the collective vibration modes and intermolecular vibration, and these fingerprint spectra can be used to identify the samples. Our research indicates that it is feasible to detect pesticide residue by using terahertz technology, and THz-TDS technique is a promising technique for pesticide residue analysis.