Researchers from the University of São Paulo (USP) have developed an electrochemical kraft paper sensor capable of detecting the presence of pesticides in fruits and vegetables in real time. When coming into contact with apples or cabbage, for example, the sensor, connected to an electronic device, identifies the presence and measures the amount of carbendazim fungicide – widely used in Brazil, despite being prohibited.
The work, supported by FAPESP through three projects (18/22214-6, 19/13514-9 It is 22/03758-0), involved groups from the Institutes of Physics (IFSC-USP) and Chemistry (IQSC-USP) on the São Carlos campus. The results were disclosed in the magazine Food Chemistry.
“To verify the presence of pesticides in food using conventional approaches, it is necessary to crush a sample, subject it to time-consuming chemical processes, and only then detect the substance. Wearable sensors, like the one we’ve developed for continuous monitoring of pesticide concentrations in agriculture and the food industry, eliminate the need for these complex procedures. It is much easier, cheaper, in addition to being much more reliable for a supermarket, restaurant or importer to carry out the verification”, he says. Osvaldo Novais de Oliveira Junior professor at IFSC-USP.
The new device has great sensitivity and resembles glucose meters [glicosímetro] used by diabetics. To measure the amount of pesticide in food, the electrochemical sensor captures the presence of the fungicide and the result can be accessed, in a matter of minutes, through a cell phone application.
“In the tests we carried out, the device had sensitivity similar to that of the conventional method. All in a faster and cheaper way”, says José Luiz Bott Neto postdoctoral fellow and corresponding author of the article describing the development of the tool.
How it works
As Bott Neto explains, the device is basically a paper substrate modified with carbon ink and submitted to an electrochemical treatment in an acid medium for the activation of carboxylic groups – which allows detection.
“We use the same system used in serigraphy [estamparia de roupas] to transfer the conductive carbon ink to the kraft paper strip, thus creating a device based on electrochemistry. The device is made with three carbon electrodes and immersed in an acid solution to activate the carboxylic groups. In other words, oxygen atoms are added to the structure of the carbon electrode. Upon contact with a sample contaminated with carbendazim, the sensor induces an electrochemical oxidation reaction that allows detection of the fungicide. Thus, the amount of carbendazim is measured via electric current”, explains Bott Neto to FAPESP Agency.
To develop the device, the researchers evaluated the stability and the impact of the paper structure on the construction of the sensors. “In addition to the development of the device, part of the work focused on understanding the issue of the properties of paper in the manufacture of the device”, says the postdoctoral fellow. Thiago Serafim Martins.
Best choice
The researchers analyzed two types of paper: kraft and parchment. Both proved to be stable enough for the construction of sensors. However, according to Martins, the porous nature of kraft paper provided greater sensitivity to the sensor and to the carboxylic groups formed during electrochemical activation.
He explains that the manufacture of electrodes in paper opens the possibility for several applications. “There are commercial electrodes made with plastic or ceramic. In our work, we managed to develop electrochemical sensors with paper, a much more malleable material, which expands its use in several fields, not just in agriculture or the food sector, but in other areas such as health, for example”, he says. .
The article Optimized paper-based electrochemical sensors treated in acidic media to detect carbendazim on the skin of apple and cabbage can be read at: www.sciencedirect.com/science/article/abs/pii/S0308814623000456?via%3Dihub.