Simultaneous determination of direct yellow 50, tryptophan, carbendazim, and caffeine in environmental and biological fluid samples using graphite pencil electrode modified with palladium nanoparticles

The present study reports the development of graphite pencil electrode modified with palladium nanoparticles (PdNPs) and its application as an electrochemical sensor for the simultaneous detection of direct yellow 50, tryptophan, carbendazim and caffeine in river water and synthetic urine samples. The combination involving the conductive surface of the graphite pencil electrode (GPE) and the enlargement of the surface area caused by the use of palladium nanoparticles (PdNPs) led to the improvement of the analytical performance of the proposed device. The surface of the GPE-PdNPs was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The charge transfer kinetics of the electrode was evaluated based on the elec-trochemical analysis of the potassium ferricyanide redox probe. Using square wave voltammetry (SWV), welldefined and fully resolved anodic peaks were detected for the analytes, with peak-to-peak potential separation not less than 200 mV. Under optimised conditions, the following linear range concentrations were obtained: 0.99-9.9 mu mol L-1 for direct yellow 50; 1.2-12 mu mol L-1 for tryptophan; 0.20-1.6 mu mol L-1 for carbendazim; and 25-190 mu mol L-1 for caffeine. The sensor showed good sensitivity, repeatability, and stability. The device was successfully applied for the determination of analytes in urine and river water samples, where recovery rates close to 100% were obtained. Due to its low cost and reusability by simple polishing, the sensor has strong potential to be used as an electrochemical sensor for the determination of different analytes.

Automated summary

The study introduced a graphite pencil electrode modified with palladium nanoparticles for the simultaneous detection of direct yellow 50, tryptophan, carbendazim, and caffeine in river water and synthetic urine samples. The device showed improved analytical performance due to the combination of the conductive surface of the graphite pencil electrode (GPE) and the enlarged surface area from palladium nanoparticles (PdNPs). The sensor, characterized by SEM and EDS, exhibited good sensitivity, repeatability, and stability with well-defined anodic peaks detected using square wave voltammetry.