Gold nanoparticle decorated multiwalled carbon nanotube modified electrodes for the electrochemical determination of theophylline

A novel and easy to prepare electrochemical sensor for theophylline (TP) determination was developed based on a new conductive platform prepared by direct dispersion of gold nanoparticles (AuNP) on a multiwalled carbon nanotube (MWCNT) network prior to deposition on a glassy carbon electrode (GCE). Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy were used to characterize the system. The modified electrode (AuNP-MWCNT/GCE) exhibited good promotion of the electrochemical oxidation of TP, factors such as solution pH, amount of MWCNT, and accumulation time and potential being optimised. Under the best conditions, the oxidation peak current of TP was linearly proportional to concentration in the range 0.5-20 mu M and the limit of detection (LOD) was estimated to be 90 nM. The developed method showed good reproducibility and excellent selectivity. Furthermore, the sensor was successfully applied to the determination of TP in pharmaceutical tablets and tea samples with excellent recoveries.