Polyphenol Detection in Mate Tea Samples Using Iron Tetrasulfonated Phthalocyanine Modified Screen-Printed Electrode

Fast, inexpensive, and efficient methods to determine polyphenols content are of interest to the food industry. Here, we propose an easy and fast sensor for the determination of polyphenol content in tea samples from a green and roasted mate. The screen-printed carbon electrodes (SPCEs) were modified with iron tetrasulfonated phthalocyanine (FeTsPc) solutions prepared at different pHs (2.5, 6.0, and 9.0). The modification in different pHs showed only small changes on catechol oxidation. However, all modified electrodes decreased the oxidation potential of catechol in comparison with unmodified SPCE. The SPCE/FeTsPc was evaluated as a sensor in catechol standard solution, showing a limit of detection and quantification of 0.6 and $2.0~\mu $ mol/L, respectively. The determination of polyphenols in the tea samples is in agreement with the Folin-Ciocalteu method; both methods used catechol as standard. The statistics results indicate SPCE modified with FeTsPc showed a high level of confidence to the application as a sensor for polyphenol content in mate tea samples.