Supplemental Data for
Differential pulse anodic stripping voltammetric determination of Cd and Pb at a bismuth glassy carbon electrode modified with Nafion, poly(2,5-dimercapto-1,3,4-thiadiazole) and multiwalled carbon nanotubes
Xiuhui He · Zhaohong Su · Qingji Xie · Chao Chen · Yingchun Fu · Li Chen · Ying Liu ·
Ming Ma · Le Deng · Dilan Qin · Yueping Luo · Shouzhuo Yao
Table S1. Limits of detection of Cd2+ and Pb2+ by anodic stripping techniques at Bi film modified electrodes*
(µg L-1) / Reference
Cd2+ / Pb2+
Bi/Nafion/PDMcT-MWCNTs/GC / DPV / 0.03 / 0.05 / This work
Bi-coated carbon electrode / SWV / 0.3 / [15]
Bi/GC / SWV / 0.2 / 0.2 / [21]
Bi/CNT / SWV / 0.7 / 1.3 / [31]
Bi/Nafion/GC / SWV / 0.1 / 0.1 / [19]
Bi/Nafion/2,2-bipyridyl/GC / SWV / 0.12 / 0.077 / [42]
Bi/ABTS-MWCNTs/GC / DPV / 0.2 / 0.1 / [36]
Bi-modified boron-doped diamond electrode / SWV / 0.18 / [20]
Bi-modified zeolite doped carbon paste electrode / DPV / 0.08 / 0.1 / [23]
Bi-powder modified carbon paste electrode / SWV / 1.2 / 0.9 / [22]
* Numbering of the references here is the same as in the main text.
Fig. S1. SEM images of the PDMcT-MWCNTs (A), PDMcTRed-MWCNTs (B) and Nafion/PDMcTRed-MWCNTs (C) surfaces. Bar length=100 nm. Here, many MWCNTs are seen in panels A and B, PDMcT-MWCNTs (panel A) shows smaller porosity between MWCNTs due to deposition of PDMcT on them, and after the electroreduction and partial dissolution of PDMcT (PDMcTRed-MWCNTs, panel B), an increased porosity between MWCNTs is seen. After the modification of an outer layer of Nafion (Panel C), the MWCNTs are almost invisible.
Fig. S2. Effects of solution pH (A), Bi3+ concentration (B), deposition potential(C), and deposition time (D) on the stripping current of Cd2+ and Pb2+ at Bi/Nafion/PDMcT-MWCNTs/GCE. The solution was 0.1 mol L-1 acetate buffer containing 10 g L-1Cd2+,10 g L-1Pb2+ and 400 g L-1Bi3+ (pH 5.0), and the preconcentration potential and time were -1.0 V and 360 s, respectively, except for the optimizing parameter.
Explanation of Fig. S2.The DPASV behaviors at Bi/Nafion/PDMcT-MWCNTs/GCE in 0.1 M acetate buffer containing 10 µg L-1 Cd2+ and Pb2+, and 400 µg L-1 Bi3+ (pH 3.0-6.0) were examined, as shown in Fig. S2. The stripping peak current increased as pH rose from 3.0 to 5.0, and then decreased gradually at higher pH, thus pH 5.0 was selected. The effects of Bi3+ concentration on the peak currents of Cd2+ and Pb2+ were studied in the range from 100 to 600 µg L-1 Bi3+, and the optimal concentration of bismuth was 400 µg L-1. When the concentration of Bi3+ was larger, bismuth will hold back the target metals and affect their peak currents. On the contrary, when the concentration of Bi3+ was lower than the optimal concentration, it cannot fully form multicomponent “fusing” alloys with the target metals. The effect of the deposition potential was studied in the potential range from -0.90 to -1.30 V, and an optimal potential of -1.0 V is recommended here. The effect of the deposition time was tested; the stripping response increased linearly with the increase in the deposition time at first, and after 360 s the stripping signal increased a little. Taking both the sensitivity and the time efficiency into account, the deposition time of 360 s was chosen in the experiments.
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