Nafion/multi-wall carbon nanotubes composite film coated glassy carbon electrode for sensitive determination of caffeine

A Nafion/multi-wall carbon nanotubes (MWNTs) composite film-modified electrode was fabricated and applied for the sensitive and selective determination of caffeine. Multi-wall carbon nanotubes (MWNTs) were easily dispersed homogeneously into methanol by ultrasonication in the presence of 0.1% Nafion. After evaporating the methanol, a Nafion/MWNTs composite film-modified electrode was achieved. Caffeine can be effectively accumulated at Nafion/MWNTs composite film-modified electrode and produce a sensitive anodic peak at around 1330 mV (vs. SCE) in a 0.01 mol L−1 H2SO4 medium (pH 2.0). Compared to the bare electrode and Nafion film-modified electrode, the Nafion/MWNTs film-modified electrode can remarkably increase the anodic peak current of caffeine. Under the suitable conditions, the anodic peak current was linear to caffeine concentration in the range of 6.0 × 10−7−4.0 × 10−4 mol L−1, and the limit of detection was 2.3 × 10−7 mol L−1. The Nafion/MWNTs composite film-modified electrode can be renewed by repetitiously cycling in a blank solution for about three cycles. This newly exploited method was successfully used to determine caffeine in beverage samples.