Utilization of electrochemical methods in determination of trace elements in beverages

Electrochemical methods have many inherent advantages such as simplicity, low cost and amenability to miniaturization. A new, sensitive and selective electrochemical method for the caffeine determination using boron doped diamond electrode was developed. It was found by cyclic voltammetry that caffeine provided highly reproducible and well-defined irreversible oxidation peak, at very positive potential of +1.55 V vs. Ag/AgCl electrode. The effect of pH and scan rate on the voltammetric response of caffeine oxidation were studied to select the optimum experimental conditions. Linear response of peak current on the concentration in the range from 4 × 10^-7 to 2.5 × 10^-5 mol L^-1, good repeatability (RSD of 2.1 %) and the detection limit of 1.5 × 10^-7 mol L^-1 without any chemical modifications and electrochemical surface pretreatment were observed by differential pulse voltammetry in 0.4 mol L^-1 perchloric acid. The effect of possible interfering compounds appeared to be negligible which evidently proved very good selectivity. The proposed method was successfully applied for the caffeine determination in commercially available beverage samples, with results in a close statistical agreement to these declared by manufacturer.