Spectroscopic investigations of a commercial graphite screen printed electrode modified by bismuth oxide drop deposition and electrochemical reduction, for cadmium and lead ions simultaneous determination

A single use graphite screen-printed electrode (GSPE) was easily modified, to take advantage of the proven affinity of the nontoxic post-transition metal bismuth (Bi), for metal ions to be detected by Square Wave Anodic Stripping Voltammetry (SWASV). A bismuth oxide (Bi2O3) or a chitosan coated (CS@Bi2O3) nanopowder suspension was drop-casted on the graphite working electrode (WE) surface, giving rise to the precursor of a Bi-modified GSPE. After that, an electrochemical reduction was performed to obtain the Bi– or the CS@Bi–GSPE. X-ray photoelectron spectroscopy and micro-X-ray fluorescence investigations were performed on the graphitic structure pre and post modification. The bismuth oxide deposition amount was considered as critical parameter to sensor performance, indicating a minimum and maximum threshold. Under improved measurement conditions, with a 300 s pre-concentration time, the attained sensors exhibited a linearity in the range (2.0–20.0) μg L−1 in the simultaneous analysis of Pb(II) and Cd(II). The Bi–GSPE showed LODs of 1.7 and 0.5 μg L−1 for Cd(II) and Pb(II) respectively, while 1.5 μg L−1 for Cd(II) and 0.2 μg L−1 for Pb(II) were recorded by the CS@Bi–GSPE. As an applicative proof in real sample, a spike test was carried out in a ground water sample, without any preliminary sample treatment.