New Kraft Paper-Based Electrochemical Sensor to Detect Traces of Pesticides in Fruit and Vegetables

At the University of São Paulo (USP) in Brazil, scientists have come up with a kraft paper-based electrochemical sensor that has the potential to detect traces of pesticides present in vegetables and fruit in real time when coupled to an electronic device.

In a cabbage or an apple, for instance, it could detect carbendazim, a fungicide that has been extensively utilized in Brazil—in spite of being banned.

Financial support was given by FAPESP for the research behind the invention. It was provided through three projects (18/22214-6, 19/13514-9, and 22/03758-0) and involved the research teams at the São Carlos Physics Institute (IFSC-USP) and São Carlos Chemistry Institute (IQSC-USP). The outcomes are reported in an article published in the Food Chemistry journal.

To find out whether a food sample contains traces of pesticides by conventional methods, you must grind up the sample and submit it to time-consuming chemical processes before any such substances can be detected.

Osvaldo Novais de Oliveira Junior, Penultimate Author and Professor, São Carlos Physics Institute

Junior added, “Wearable sensors like the one we developed for continuous monitoring of pesticides in agriculture and the food industry eliminate the need for these complex processes. Inspection is much easier, cheaper, and reliable for a supermarket, restaurant, or importer, for example.”

The new device is extremely sensitive and looks like the glucometers that have been used by diabetics to measure blood sugar, except that the outcomes of food scanning for pesticides are displayed on a smartphone.

In the tests we performed, its sensitivity was similar to the conventional methods. Plus, it’s fast and inexpensive.

José Luiz Bott Neto, Study Corresponding Author and Postdoctoral Fellow, São Carlos Physics Institute

How It Works

The device comprises a paper substrate altered with carbon ink and provided electrochemical treatment in an acid medium to trigger carboxyl groups and make detection feasible, explained Bott Neto.

We use the silkscreen process to transfer carbon-conducting ink to a strip of kraft paper, thereby creating a device based on electrochemistry. It has three carbon electrodes and is immersed in an acidic solution to activate the carboxyl groups. In other words, oxygen atoms are added to the structure of the carbon electrode.

José Luiz Bott Neto, Study Corresponding Author and Postdoctoral Fellow, São Carlos Physics Institute

Neto added, “When it comes into contact with a sample contaminated with carbendazim, the sensor induces an electrochemical oxidation reaction that permits detection of the fungicide. The quantity of carbendazim is measured via electrical current.”

The scientists assessed the stability and structure of the paper substrate while developing the device. “The properties of the paper itself were an important part of our research,” stated Thiago Serafim Martins, first author of the article and a postdoctoral fellow at IFSC-USP.

Best Option

Kraft paper and parchment were examined by the scientists, finding both kinds of paper to be highly stable to act as a substrate for the sensor.

But the porousness of kraft paper conferred high sensitivity on the sensor and the carboxyl groups developed at the time of electrochemical activation, explained Martins. This adds to the fact that paper-based electrodes could be utilized in numerous applications.

Martins added, “There are commercial electrodes made of plastic or ceramic material. We successfully developed electrochemical sensors based on paper, a much more malleable material and therefore potentially useful in many areas, not just on farms or in supermarkets, but also in healthcare, for example.”

Journal Reference:

Martins, T. S., et al. (2023) Optimized paper-based electrochemical sensors treated in acidic media to detect carbendazim on the skin of apple and cabbage. Food Chemistry. doi.org/10.1016/j.foodchem.2023.135429.