Electrodes with extremely high hydrogen overvoltages as substrate electrodes for stripping analysis based on bismuth-coated electrodes

Effect of Bi(iii)-to-metal ion concentration ratios on stripping voltammetric response of bismuth-film glassy carbon electrodes

The effect of Bi-to-metal ion concentration ratio (c Bi/c M ratio) on key evaluation indicators, including sensitivity, precision, and cathodic potential range, has been investigated for the determination of Cd and Pb at in situ prepared bismuth film electrodes. Unlike the usual recommendation of at least a 10-fold excess of Hg(ii) for anodic stripping experiments at in situ prepared mercury film electrodes, it is found that the c Bi/c M ratios in the 1-10 range are sufficient to obtain a high determination sensitivity, but that the signal decreases significantly when the ratio exceeds 40. Further analysis shows that the precision of the analytical results is good when the c Bi/c M ratio is in the range of 5-10. The precision is even better in the range of 10-20, but too high a ratio cannot further improve the precision of the results. Therefore, it is recommended to keep the c Bi/c M in the range of 5 to 40 to balance the sensitivity and precision in detection. The study also finds that the optimum cathodic potential range is related to the total concentration of metal ions. Therefore, for metals susceptible to hydrogen evolution (e.g., zinc), additional consideration should be given to inhibiting the hydrogen evolution reaction when selecting the c Bi/c M ratio. This work is the first to investigate the effect of the c Bi/c M ratio on the morphology and thickness of deposits using EIS, SEM, and AFM. It is found that increasing the c Bi/c M ratio leads to an increase in the coverage and thickness of the bismuth film on the electrode surface, which enhances the sensitivity of the determination. However, this change is also accompanied by an increase in the electrode resistance, resulting in a significant decrease in signal when the ratio is too large. In addition, when the c Bi/c M ratio is <5, the precision of the bismuth film electrode is relatively poor due to the rapid increase of the bismuth coverage on the electrode surface. The uneven thickening of the deposit also affects the cathodic potential range. Based on these findings, standard curves with c Bi/c M ratios ranging from 5-25 are prepared and successfully applied to the analysis of river water and wastewater.

Recent development of carbon electrode materials and their bioanalytical and environmental applications

New synthetic approaches, materials, properties, electroanalytical applications and perspectives of carbon materials are presented.

Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples

A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N'-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, -1.100 V vs. Ag/AgCl; deposition time, 60s; resting time, 10s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL(-1) for the determination of Cd(2+), Cu(2+) and Hg(2+), respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd(2+), Cu(2+) and Hg(2+). Furthermore, the present method was applied to the determination of Cd(2+), Cu(2+) and Hg(2+) in water and some foodstuff samples.