An adsorptive stripping voltammetric study based on disposable pencil graphite sensor for the determination of caffeine in local brand ice tea

Abstract

In this study, voltammetric methods were developed for the quantification of caffeine (CAF) analysis based on a practical, economical, sensitive, and eco-friendly pencil graphite electrode (PGE). Initially, the electrochemical behavior of CAF was investigated by cyclic voltammetry (CV), and the results reveal that CAF has an irreversible oxidation signal. The optimum analytical parameters such as, supporting electrolyte, pH, accumulation potential, and accumulation time for the determination of CAF analysis were investigated to develop differential pulse (AdsDPV) and square wave adsorptive stripping voltammetric (AdsSWV) methods. In order to examine the nature of the buffer, Britton Robinson (BR), phosphate buffer (PBS), and 0.1 M H2SO4 solutions were tested in the appropriate pH ranges. The best electrolyte and pH were determined as PBS buffer and pH 1.5. The optimum values for accumulation potentials and times were optimized, and under optimized conditions, the oxidation peak current of CAF was proportional to its concentration. The PGE used exhibited wide linear working range for AdsDPV (2.36-1000 µM) and AdsSWV (3.69-1600 µM) methods with the detection limits of 0.71 µM for AdsDPV and 1.107 µM for AdsSWV. The developed methods were applied to the analysis of CAF in an ice tea beverage sample with acceptable recoveries.