Characterization of iron-modified carbon paste electrodes and their application in As(V) detection

Here graphite powder modified with iron hydro(oxide) particles was used to prepare carbon paste electrodes for the determination of arsenic (As). The modified material was easily prepared using the slurry method and characterized by Brunauer-Emmett-Teller surface area and pore size distribution, surface charge distribution, point of zero charge, X-ray diffraction, and potentiometric titration. Adsorption experiments with the modified material showed good arsenic removal capacity, even in the presence of NaNO3 salt used as electrolytic media in electrochemical experiments. The detailed physicochemical characterization of the iron-modified carbon paste and the determination of its adsorption capacity allowed the understanding of the arsenic detection process on the electrode surface. The electrochemical detection of As(V) was investigated by differential pulse voltammetry technique using iron-modified carbon paste electrodes. The method was performed based on the stripping oxidation of zero-valent arsenic deposited at the electrode surface after its pre-concentration at -1.10 V for 180 s. The As(V) was reduced on modified electrodes at pH 2.5. Linear calibration curve was achieved for a series of concentrations from 25 to 1000 mu g L-1 for a standard solution of As(V) (r (2) = 0.99). Detection limit of 10 mu g L-1 can be achieved for As(V). Reproducibility was shown for stripping voltammetry of this species with an RSD (n = 8) of 7.5 %.