Electrochemical Determination of Gallic Acid in Tea Samples Using Pyramidal Pt Nanoparticles

Gallic acid (GA) is a natural phenolic compound with significant biological properties, including anti-inflammatory, antioxidant, and anticancer effects. Detecting GA in biological matrices like food and beverages is essential but challenging due to the multitude of GA-like molecules with similar proprieties and functional moieties. In this study, ultra-small (≈4 nm) pyramidal platinum nanoparticles (PtNPs) with a high fraction of {111} surface domains are used to design a new electrochemical sensor for GA detection in tea, which is the most popular manufactured drink consumed in the world. PtNPs are deposited on a glassy carbon electrode (GCE) using a simple drop deposition method, requiring a minimal amount of nanoparticles and, hence, metal precursor. With just 2.7 µg of PtNPs, the sensor demonstrated a linear response in the concentration range from 50 to 600 µm, a detection limit of 16 µm, and a quantification limit of 49 µm. The sensor selectivity is tested against other antioxidant compounds commonly present in tea, consistently showing a higher response for GA. Furthermore, the sensor capability to detect GA in real green and black tea samples is further validated by high-performance liquid chromatography (HPLC) analysis, with high correlation between chromatographic data and sensor response.