Scientists of the Tomsk Polytechnic University have designed an express method of visual testing of food products for the content of heavy metals, trace elements, nitrates and antioxidants, the TPU press service reports. It is meant for vegetables and fruits mainly, as well as beverages. For the test, little transparent sensors of modified Plexiglas are used. When interacting, for example, with molecules of heavy metals, the sensors change their color. By the intensity of color, one can establish the concentration of the detected substance.

“In Russia, the “Strategy for improving the quality of food products in the Russian Federation till 2030” has been adopted at the federal level. It involves the expansion of a range of simple and fast methods for analyzing products, not only for specialized laboratories, but also for domestic needs. In addition, the natural need of a person is the willingness to know what they are eating and drinking. We have developed a method of non-instrumental visual analysis, so that each person could independently check food products for various indicators with high accuracy, without using special instruments and without resorting to laboratories. For this we use "polymethylmethacrylate" – that is organic glass. We modify it in such a way that the polymer acquires 3D structure, thus enabling us to insert other reagents interacting with heavy metals, nitrates, antioxidants or trace elements in it. Upon contact with useful or toxic substances, the initially transparent colorless polymer changes its color”, - the project's scientific adviser, professor of the Engineering School of Natural Resources Mikhail Gavrilenko says.

This modified plexiglass belongs in the class of "breathing" polymers, literally absorbing the target substance within a few minutes. All it takes to make the test is to put the sensor platelet into the pulp of mashed product. If there are nitrates in an apple, for example, the platelet will turn yellow-brown, and if heavy metals, it will be the more red, the higher their content.

Such a simple method of visual identification has been certified by the Federal Agency for Technical Regulation and Metrology and included in the register of the Federal Information Foundation for ensuring the uniformity of measurements.

“Reagents are inserted right into the transparent platelet, but they are not a functional group of the polymer; in this case the polymer is just a cellular reagent container. To date, this approach surpasses the world level. It is done differently abroad - each time for a specific task, the reagents are embedded in the polymer as a functional group. Another foreign approach is to mix polymers and reagents into unstable gel structures. Hence is a number of problems, including the fact that not every reagent can be embedded in the structure. This makes foreign counterparts unstable. Our polymer sensors, however, can be stored for a very long time without losing their properties,” - the scientist notes.

The cost of one polymer sensor for on-site analysis is not more than several tens of rubles, which is 20-30 times cheaper than the traditional method of spectrophotometry. By the way, the color platelets preserved after use can be applied afterwards in conventional photometric equipment to confirm the results of the visual testing.