High sensitive determination of theophylline based on gold nanoparticles/l-cysteine/Graphene/Nafion modified electrode

In the work described on this paper, a gold nanoparticles (GNP)/l-cysteine (l-cys)/Graphene (Gr)/Nafion composite film modified glass carbon electrode (GCE) was fabricated and characterized. The modified electrode showed excellent electrocatalytic activity towards the oxidation of theophylline (TP) in 0.1 mol L−1 H2SO4 medium. Differential pulse voltammetry (DPV) was used for the determination of TP. Under the optimum conditions, the peak current of TP was proportional to its concentration at the range of 4.0 × 10−9 to 6.0 × 10−5 mol L−1 with a detection limit 4.0 × 10−10 mol L−1. The newly developed method was successfully applied for the determination of TP in tea samples and pharmaceutical tablets with good percentage of recoveries.