A simple and compact colour sensor based on conventional plexiglass is able to replace laboratory tests in measuring of antioxidants, according to a study in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Journal.
Many food products, dietary supplements and medicinal plant extracts contain biologically active antioxidants that slow down or inhibit processes in the body which harm human health. Up until now, scientists have assessed their antioxidant capacity using laboratory methods on specialised electrochemical or photometric equipment.
But the researchers have come up with a compact and inexpensive analogue to replace the existing method: antioxidant capacity is determined by the intensity of the colour of the sensor, which depends on the number of antioxidants in the sample.
“We have developed a miniature domestic sensor. It is a transparent polymer plate the size of a small coin that changes colour when it comes into contact with liquids that have antioxidants. With its help, anyone can determine the antioxidant properties of a product. Moreover, the sensor is compatible with modern analytical equipment, which then allows domestic results to be double-checked in the laboratory”, Mikhail Gavrilenko, a professor at the Division for Chemical Engineering of the TPU School of Earth Sciences and Engineering, said.
The researchers used an organic compound, Cu(II)–neocuproine, to assess antioxidant capacity. When the system interacts with an antioxidant, an oxidation-reduction (redox) reaction to Cu(I) occurs, which together with neocuproine turns the sensor yellow. The findings helped to build a model for linking general antioxidant capacity to the concentration of phenolic substances in the sample.
According to Gavrilenko, colour analysis of antioxidant capacity is usually carried out in solutions or gels, but their instability makes it hard to reproduce results and impossible to cross-check.
What makes the Tomsk scientists' approach unique is the structure of the polymer shows all the properties of the liquid except for its own solid-state. Using the standard plexiglass (polymethylmethacrylate) as a basis, the scientists change its structure so that its plates change colour when in contact with a predetermined substance.
“Just as millions of chemical reactions can take place in water, so the 'solid water' of our polymer has endless possibilities for running 'coloured' chemical reactions with virtually any given substance. We have never once encountered the impossibility of running a selected 'coloured' chemical reaction in [this new] environment,” Gavrilenko explained.
The scientists also plan to develop specific software for smartphones, which could identify the substance and estimate its quantity by any user using a photo of the sensor. Such a system would allow for extensive use of off-lab rapid analysis in various fields of activity.