Fullerene-based anodic stripping voltammetry for simultaneous determination of Hg(II), Cu(II), Pb(II) and Cd(II) in foodstuff

Various carbon nanomaterials for use in anodic stripping voltammetric analysis of Hg(II), Cu(II), Pb(II) and Cd(II) are screened. Graphene, carbon nanotubes, carbon nanofibers and fullerene (C-60), dispersed in chitosan (Chit) aqueous solution, are used to modify a glassy carbon electrode (GCE). The fullerene-chitosan modified GCE (C-60-Chit/GCE) displays superior performance in terms of simultaneous determination of the above ions. The electrodes and materials are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The excellent performance of C-60-Chit/GCE is attributed to the good electrical conductivity, large surface area, strong adsorption affinity and unique crystalline structure of C-60. Using differential pulse anodic stripping voltammetry, the assay has the following features for Hg(II), Cu(II), Pb(II) and Cd(II), respectively: (a) Peak voltages of +0.14, -0.11, -0.58 and -0.82 V (vs SCE); (b) linear ranges extending from 0.01-6.0 mu M, 0.05-6.0 mu M, 0.005-6.0 mu M and 0.5-9.0 mu M; and (c), detection limits (3 sigma method) of 3 nM (0.6 ppb), 14 nM (0.9 ppb), 1 nM (0.2 ppb) and 21 nM (2.4 ppb). Moreover, the modified GCE is well reproducible and suitable for long-term usage. The method was successfully applied to the simultaneous determination of these ions in spiked foodstuff.