Voltammetric determination of caffeine by using gold nanoparticle-glassy carbon paste composite electrode

In the present study, simple and sensitive voltammetric determination of caffeine was carried out by using a gold nanoparticle-glassy carbon paste composite electrode (AuNP-GCPE) in 3.2 mM H2SO4 (pH 2.5). The effects of supporting electrolyte, pH and AuNP amount on caffeine peak current were investigated. After the optimization of experimental parameters, analytical characteristics of AuNP-GCPE were examined and two linear ranges were obtained between 25-150 μM and 200-1000 μM with limit of detection values of 0.96 μM and 4.90 μM, respectively. Relative standard deviation for 50 μM caffeine was also calculated as 7.52% (n = 3). In order to evaluate the analytical performance of AuNP-GCPE, caffeine contents of various brands of cola samples were measured and compared with the results obtained by UV-Vis spectrometer. The obtained results by using the proposed composite electrode are in accordance with the caffeine contents that manufacturers claimed compared to UV-Vis. This composite electrode which utilizes the catalytic effect of AuNP with the simple preparation of GCPE, offers a fast and sensitive determination of caffeine in beverages as a practical application.