The P=O and P=S
groups of organophosphorus pesticides have extremely high Raman activity, so
the detection of organophosphorus pesticide residues by Raman spectroscopy is a
very efficient and nondestructive means. However, surface enhanced Raman
spectroscopy (SERS), which is commonly used at present, is difficult to be
applied to high precision quantitative pesticide residue detection due to the
lack of standardized substrate and pretreatment technology. The novel ultra-low
frequency Raman spectroscopy can effectively detect the low-frequency Raman
peak (0-500cm^-1) that is more sensitive to the concentration.
Therefore, this paper studied the frequency and intensity changes of low
frequency Raman peaks of two representative organophosphorus pesticides
chlorpyrifos and trichlorfon at different concentrations, and accurately
identified each low frequency vibration mode. In addition, we can accurately
identify the concentration by establishing the dependence of the concentration
of two types of pesticides on the vibration frequency and intensity. The lowest
detectable limits of ultralow frequency Raman technique in the detection of
chlorpyrifos and trichlorfon are 0.012 mg/kg and 0.25 mg/kg respectively, which <a name="_Hlk121747729"></a>basically meet the requirements
of the national standard, and provides a preliminary and new experimental idea
for the detection of food pesticides.