Sensitive determination of trace Cd(ii) and Pb(ii) in soil by an improved stripping voltammetry method using two differentin situplated bismuth-film electrodes based on a novel electrochemical measurement system

Abstract

In this study, a simple but effective electrochemical method was developed to minimize the interference from real soil samples and increase the sensitivity of Pb(II) and Cd(II) detection by square-wave anodic stripping voltammetry (SWASV) using a novel electrochemical measurement system, which can be used for the onsite determination of trace Cd(II) and Pb(II) in real soil samples. The method involved performing SWASV following double deposition and stripping steps at two in situ plated bismuth-film electrodes with drastically different surface properties. Pb(II) and Cd(II) were first deposited on an in situ plated bismuth-film graphite carbon paste electrode (Bi/GCPE). When the first deposition was finished, the GCPE was moved to a micro-electrolytic cell to perform the first stripping step. The following measurements were performed with the other deposition and stripping steps using a highly sensitive in situ plated bismuth-film multiwalled carbon nanotube-Nafion composite modified glassy carbon electrode (Bi/MWCNT-Nafion/GCE) as the working electrode. Pb(II), Cd(II) and Bi(III) stripped from the GCPE in the micro-electrolytic cell were partially deposited on the MWCNT-Nafion/GCE, and the stripping current signals were obtained from their oxidation during the second stripping step. Considering the small volume of the micro-electrolytic cell, the concentrations of Cd(II) and Pb(II) were drastically higher than those in the bulk solution, and therefore, the detection limits were reduced. Under the optimized conditions, the concentrations in the linear range spanned from 1.0 to 45.0 mg L À1 for both Pb(II) and Cd(II), with a detection limit of 0.03 mg L À1 for Pb(II) and 0.02 mg L À1 for Cd(II) (S/N ¼ 3). Finally, analyses of real samples were performed to detect trace levels of Pb(II) and Cd(II) in soil with satisfactory results.

Disposable and Low-Cost Electrode Based on Graphene Paper-Nafion-Bi Nanostructures for Ultra-Trace Determination of Pb(II) and Cd(II)

“…The characteristic peaks of Cd 2+ and Pb 2+ are observed at −0.93 and −0.65 V vs. SCE for GP_Bi, at −0.95 and −0.67 V vs. SCE for GP_naf_Bi and at −0.91 and −0.63 V vs. SCE for GP_naf_ex_Bi, respectively. The values of stripping peaks of lead and cadmium are very close to that reported in literature [14,33]. The observed variations in the stripping potentials of Pb 2+ and Cd 2+ may be related to the variation of impedance modulus of the electrodes (as discussed later on).…”

“…Figure 4 reports typical square wave anodic stripping voltammograms obtained by GP_Bi of Pb 2+ at concentrations of 25 (red line) and 200 (black line) ppb, respectively. The voltammograms show two peaks centered at about −0.67 and −0.22 V vs. SCE that are assigned to Pb 2+ and Bi 3+ , respectively [ 14 ]. The anodic stripping peak corresponding to Bi 3+ is typically broad and exhibits asymmetry which may be attributed to different Bi phases, structures, or partial bismuth oxidation.…”

“…Lu compared the sensing performance of four kinds of nanomaterials of replacing mercury that are based on metallic nanoparticles, metal oxides, carbon nanomaterials and their nanocomposites and chelating additives for analyte metal ions [8]. However, among the various kinds of nanomaterials, bismuth-based electrodes are the most promising substitutes in the analysis of lead and cadmium by SWASV for their suitable potential working window and not-poisonous properties [11][12][13][14][15]. Numerous works described the realization of electrodes and their employment by ex-situ or in-situ co-electrodeposition of bismuth and analyte metals, consisting of modified glassy carbon [16,17], graphene oxide [18], modified multiwalled carbon nanotubes [19] and screen-printed carbon paste [20,21].…”

“…These facts lead to costly electrodes. Thus, an increasing demand for low-cost, sensitive and user friendly electrodes still exists, despite the efforts of the scientific community [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].…”

Bismuth Subcarbonate Decorated Reduced Graphene Oxide Nanocomposite for the Sensitive Stripping Voltammetry Analysis of Pb(II) and Cd(II) in Water

“…The WEs play a key role in the detection sensitivity of this method. In the past few decades, bismuth-based materials modified electrodes have gradually become a successful alternative to the mercury electrodes due to their interesting characteristics, such as low toxicity, a wide electrochemical potential window, and the ability to form alloys with heavy metals [14,15], which helps detect them at trace levels [16][17][18][19][20].…”