Co3O4 nanoparticles and multiwalled carbon nanotubes modified carbon paste electrode for determination of gallic acid using electrochemical techniques

Gallic acid, GA, is one of the main phenolic components found in black tea, grapes, and several other plants [1]. Recently, polyphenols, especially those naturally present in foods, have been a subject of increasing interest due to their biological properties,including anti-inflammatory, antihistaminic, and antitumor activities, scavenging of free radicals, and protecting against cardiovascular diseases [2]. On the other hand, GA is final product of basic hydrolysis of tannic acid present toxic effluents which cause environmental pollution [3]. Therefore, the objective of the work was to develop and apply an efficient simple sensor for rapid adsorptive stripping voltammetric determination of GA at low concentration. For this purpose, Co3O4 nanoparticles and multiwalled carbon nanotubes (MWCNTs) modified carbon paste electrode (CPE) was used as a fast and sensitive tool for the investigation of electrochemical oxidation of gallic acid. The study was carried out by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. In fact, the electrochemical behavior of Co3O4/MWCNTs /CPE was explored utilizing cyclic voltammetry and electroactive surface area (ESA) calculations. Gallic acid was detected over a linear concentration range of 0.05-20 μM by differential pulse voltammetry with correlation coefficient of 0.992. In addition, the values of LOD and LOQ for this method were derived 0.012 and 0.039 μM, respectively. It is interesting to note that the suggested sensor showed an acceptable selectivity toward gallic acid in the presence of some interferent substances, repeatability and long-term stability. Finally, the electrochemical oxidation of gallic acid at the surface of Co3O4/MWCNTs/CPE employed efficiently for the voltammetric determination of gallic acid in green and black tea and orange juice.