Sensitive Differential Pulse Stripping Voltammetry of Caffeine in Medicines and Cola Using a Sensor Based on Multi-Walled Carbon Nanotubes and Nafion

A sensitive electrochemical sensor for the determination of caffeine (3,7 – dihydro - 1, 3, 7 – trimethyl - 1H – purine - 2, 6 – dione) based on a multi-walled carbon nanotube and a Nafion-modified glassy carbon electrode (MWCNT-Nafion/GCE) using differential pulse adsorptive stripping voltammetry is presented. The surface micromorphology of the MWCNT-Nafion/GCE as well as the effects of pH, scan rate, accumulation potential and time were investigated by scanning electron microscopy, atomic force microscopy and other electrochemical techniques. At optimal test conditions, the calibration curves for the determination of caffeine showed two linear responses. The first linear range was from 2.945 to 377.0 μM, with a detection limit of 0.513 μM (based on 3σ), and the second linear range was from 377.0 to 2356 μM. The sensor was then successfully utilised for the determination of caffeine in real samples of “Sanlietong” tablets and Cola.