A carbon paste electrode improved with poly(ethylene glycol) for tannic acid surveillance in beer samples.

Tannic acid is often used as additive in beers and is an important parameter to be evaluated in quality control of beverages. Thus, this paper describes the improvement of a carbon paste electrode through its modification with poly(ethylene glycol) for determination of tannic acid in beers. Microscopic and electrochemical techniques were used to characterize the modified surface. The electrochemical behavior of tannic acid and the optimization of experimental parameters (pH, supporting electrolyte and accumulation step) on the modified surface were performed by cyclic voltammetry. The calibration plot for tannic acid by differential pulse voltammetry was linear in the range of 0.08-2.10 µmol L-1 with limits of detection and quantification of 72.6 and 220 nmol L-1, respectively. Lastly, the carbon paste electrode improved with poly(ethylene glycol) was effectively implemented in the quantification of tannic acid in beer samples. The results were similar to those furnished by the Folin-Ciocalteu method.