Rapid identification of some toxins by Raman spectroscopy in agricultural export products of Vietnam
Identifying residues (trace amounts) of toxic chemicals remaining in agricultural and food products is very difficult. Although some of the methods used are highly accurate in determining residues of hazardous substances, these methods are often expensive and time consuming, require highly specialized users, and the machinery and equipment are complicated, so it is hard to apply these as common methods to quickly identify toxic residues in export agricultural products of our country. In the past decade or so, Raman spectroscopy has gradually become a good candidate for the identification of organic molecules due to its fast results, low cost and the ability to preserve samples. However, the limitation of Raman spectroscopy remains the sensitivity of the method.
To overcome this problem, surface-enhanced Raman spectroscopy (SERS) was proposed and developed to detect traces (with concentrations in the parts per million to parts per billion (ppm-ppb)) of many substances (especially organic substances) on different substrates. The development of high-sensitivity SERS substrates, the application of surface-enhanced Raman spectroscopy to identify toxins in agricultural products for export, is a necessity, bringing great long-term benefits.
Figure 1. Fabrication process of surface-enhanced Raman substrates from cicadas wings and applications in Raman spectroscopy
In this study, the research team initially built up spectral data of 23 compounds, including 10 plant protection chemicals, 06 growth-promoting compounds, 02 growth-inhibiting compounds, and 05 growth-inhibiting compounds. These are typical compounds to be used to expand the database for the analysis of other compounds in exported agricultural products in the future.
The project also succeeded in making SERS substrates from silver nano-coated cicadas wings and PDMS/Ag-AgNPs substrates simulating rose petal structure with a stable, inexpensive process but still bringing the desired effect. The signal enhancement ability of the SERS substrates is up to 4.7 x 107. Since then, these SERS substrates are used to detect plant protection compounds, growth promoting compounds and bioinhibitory compounds as well as mold on standard samples and on Vietnamese agricultural products such as analysis of permethrin, paraquat in watermelon, difenoconazole in potato, imidacloprid, acetate and carbaryl in mango. Besides, the study also succeeded in analyzing all three substances imidacloprid, acephat and carbaryl simultaneously in mango. The results make an important contribution to scaling up the application of the SERS method to simultaneously detect many toxins in agricultural exports of Vietnam in the coming time.
Figure 2: Process for making surface-enhanced Raman substrates from rose petals and their application in Raman spectroscopy
Research results show that it is possible to develop Raman spectroscopy libraries of compounds and toxins in agricultural products to apply Raman spectroscopy to quickly detect these compounds in agricultural products in our country. In addition, the research team also recommends the development of a handheld Raman spectroscopy model to widely apply this method in the near future.
Figure 3: Portrait of Chairman Dr. Nguyen Thanh Duong
Translated by Phuong Huyen
Link to Vietnamese version
