Stripping Voltammetry with Bismuth Modified Graphite‐Epoxy Composite Electrodes

The attractive performance of graphite‐epoxy composite electrodes (GECE) surface‐modified with a bismuth film (Bi‐GECE) for simultaneous and separate stripping determination of trace amounts of heavy metals (lead, cadmium and zinc) is described. Several key parameters have been optimized. Bi‐GECEi electrode shows superior accumulation properties when compared to bare GECE or even to Hg‐GECE. Bi‐GECE exhibits well‐defined, undistorted, reproducible and sharp stripping signals with RSD of 2.99%, 1.56% and 2.19% for lead, cadmium and zinc respectively. Detection limits of 23.1, 2.2 and 600 μg/L for lead, cadmium and zinc were obtained. Sharp peaks with high resolution (of neighboring signals) that permit convenient multi‐elemental measurements resulted. The applicability of the electrodes to the real samples (tap water and soil sample) was also tested and promising results with good recoveries were obtained.     

3D‐printed Metal Electrodes for Heavy Metals Detection by Anodic Stripping Voltammetry

Heavy metals, being one of the most toxic and hazardous pollutants in natural water, are of great public health concern. Much effort is still being devoted to the optimization of the electroanalytical methods and devices, particularly for the development of novel electrode materials in order to enhance selectivity and sensitivity for the analysis of heavy metals. The ability of 3D‐printing to fabricate objects with unique structures and functions enables infinite possibilities for the creation of custom‐made electrochemical devices. Here, stainless steel 3D‐printed electrodes (3D‐steel) have been tested for individual and simultaneous square wave anodic stripping analysis of Pb and Cd in aqueous solution. Electrodeposition methods have also been employed to modify the steel electrode surface by coating with a thin gold film (3D−Au) or a bismuth film (3D−Bi) to enhance the analytical performance. All 3D‐printed electrodes (3D‐steel, 3D−Au and 3D−Bi) have been tested against a conventionally employed glassy carbon electrode (GC) for comparison. The surface modified electrodes (3D−Au and 3D−Bi) outperformed the GC electrode demonstrating higher sensitivity over the studied concentration ranges of 50–300 and 50–500 ppb for Pb and Cd, respectively. Owing to the bismuth property of binary alloys formation with heavy metals, 3D−Bi electrode displayed well‐defined, reproducible signals with relatively low detection limits of 3.53 and 9.35 ppb for Pb and Cd, respectively. The voltammetric behaviour of 3D−Bi electrode in simultaneous detection of Pb and Cd, as well as in individual detection of Pb in tap water was also monitored. Overall, 3D‐printed electrodes exhibited promising qualities for further investigation on a more customizable electrode design.     

A stannum-bismuth composite film electrode for simultaneous determination of zinc(II) and cadmium(II) using differential pulse anodic stripping voltammetry

The development and use of 'green' electrode materials is extremely attractive for the routine use of disposable metal sensors. Bismuth is an environmentally-friendly element and a bismuth film electrode was proposed as an alternative to mercury film electrodes. Compared with bismuth, stannum is a more 'environmentally friendly' material. The stannum-bismuth composite film electrode prepared by the in situ electrodeposition of stannum and bismuth on the glassy carbon substrate is reported for the first time. Compared with bismuth film and stannum film electrodes, the stannum-bismuth composite film electrode revealed better electroanalytical performance, and can be used as a possible alternative electrode for electrochemical stripping analysis of trace heavy metals.     

Bismuth/Polyaniline/Glassy Carbon Electrodes Prepared with Different Protocols for Stripping Voltammetric Determination of Trace Cd and Pb in Solutions Having Surfactants

To improve reproducibility, stability and sensitivity, a bismuth (Bi) thin film was coated on glassy carbon (GC) substrates which surfaces were modified with a porous thin layer of polyaniline (PANI) via multipulse potentiostatic electropolymerization to form Bi/PANI/GC electrodes (Bi/PANI/GCEs). The Bi/PANI/GCEs were used successfully for simultaneous detection and determination of Cd²⁺ and Pb²⁺ ions, and various parameters were studied with reference to square wave anodic stripping voltammetric (SWASV) signals. The experimental results depicted that the environment‐friendly Bi/PANI/GCEs had the ability to rapidly monitor trace heavy metals even in the presence of surface‐active compounds.     

Determination of trace amounts of lead and cadmium using a bismuth/glassy carbon composite electrode

We examined the use of a bismuth-glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1 M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 μg/L for lead and 0.49 μg/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.     

Hydrolysis of a basic bismuth nitrate--formation and stability of novel bismuth oxido clusters

The synthesis of the nanoscaled bismuth oxido clusters [Bi(38)O(45)(NO(3))(20)(DMSO)(28)](NO(3))(4)·4DMSO (1a) and [Bi(38)O(45)(OH)(2)(pTsO)(8)(NO(3))(12)(DMSO)(24)](NO(3))(2)·4DMSO·2H(2)O (2) starting from the basic bismuth nitrate [Bi(6)O(4)(OH)(4)](NO(3))(6)·H(2)O is reported herein. Single-crystal X-ray diffraction analysis, ESI mass spectrometry, thermogravimetric analysis, and molecular dynamics simulation were used to study the formation, structure, and stability of these large metal oxido clusters. Compounds 1a and 2 are based on a [Bi(38)O(45)](24+) core, which is structurally related to δ-Bi(2)O(3). Examination of the fragmentation pathways of 1a and 2 by infrared multi-photon dissociation (IRMPD) tandem MS experiments allows the identification of novel bismuth oxido cluster species in the gas phase.     

Recent Advances in Anodic Stripping Voltammetry with Bismuth‐Modified Carbon Paste Electrodes

In this article, the results of some recent investigations on two types of bismuth‐modified carbon paste electrodes are presented. In the first study, the bismuth‐film carbon paste electrode (BiF‐CPE) operated in situ and employed in anodic stripping voltammetry of Cd(II) and Pb(II) at the low μg L^?1 level was of interest in view of choosing the proper Bi(III)‐to‐Me(II) concentration ratios (where Me: Pb or Cd). Such optimization has resulted in significant improvement of detection limits down to 1.0 μg L^?1 Cd and 0.8 μg L^?1 for Pb, which allowed us to apply the BiF‐CPE for analysis of selected real samples of tap and sea water. The BiF‐CPE was also further investigated for its application in highly alkaline media. In this case, attention was focused on the complex‐forming capabilities of the OH ^– ions and their effect on the anodic stripping characteristics of some heavy metals (i.e. Cd, Pb, Tl) as well as upon the formation of the bismuth film itself. The last example deals with the continuing characterization of the recently introduced carbon paste electrodes modified with bismuth powder (Bi‐CPEs) which combine the advantageous properties of carbon paste material with the favorable electrochemical properties of bismuth. Three series of electrodes, differing either in the content of metallic bismuth (from 8 to 50% w/w) or in the type of the carbon powder used (two spectroscopic types of graphite and powdered glassy carbon), were compared and the respective relations to the optimal carbon paste composition evaluated. Attractive electroanalytical performance of the Bi‐CPE in anodic stripping voltammetry is demonstrated for selected model mixtures of heavy metals (Mn, Zn, Cd, Pb, Tl, and In).     

Ultrasensitive Voltammetric Detection of Trace Lead(II) and Cadmium(II) Using MWCNTs‐Nafion/Bismuth Composite Electrodes

Multiwall carbon nanotubes were dispersed in Nafion (MWCNTs‐NA) solution and used in combination with bismuth (MWCNTs‐NA/Bi) for fabricating composite sensors to determine trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the MWCNTs‐NA/Bi composites film modified glassy carbon electrode (GCE) were evaluated. The synergistic effect of MWCNTs and bismuth composite film was obtained for Pb(II) and Cd(II) detection with improved sensitivity and reproducibility. Linear calibration curves ranged from 0.05 to 100 μg/L for Pb(II) and 0.08 to 100 μg/L for Cd(II). The determination limits (S/N=3) were 25 ng/L for Pb and 40 ng/L for Cd, which compared favorably with previously reported methods in the area of electrochemical Pb(II) and Cd(II) detection. The MWCNTs‐NA/Bi composite film electrodes were successfully applied to determine Pb(II) and Cd(II) in real sample, and the results of the present method agreed well with those of atomic absorption spectroscopy.     

Validation of bismuth film electrode for determination of cobalt and cadmium in soil extracts using ICP-MS

A study is presented on the use of the bismuth film electrode (BiFE) operated in the anodic stripping and the cathodic adsorptive stripping voltammetry (ASV, CAdSV) modes, for the determination of two trace heavy metals (Cd and Co, respectively), in soil extract samples. Two types of BiFE were examined in this study: the in situ prepared BiFE, which was employed in ASV determination of Cd, and the ex situ prepared BiFE, which was used in CAdSV of Co with dimethylglyoxime (DMG) as complexing agent. A series of unpretreated soil extracts with varying Cd and Co concentrations were analyzed, and the results obtained compared to those determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed the suitability of stripping analysis at the BiFE for determination of μg l⁻¹ levels of heavy metals in soil extracts. The promising results obtained here, coupled with the non-toxic nature of bismuth (in comparison to commonly used mercury electrodes employed in stripping analysis), offer great promise in centralized and decentralized analysis of trace heavy metals in complex environmental matrices.     

Second harmonic a.c. anodic stripping voltammetry of metals at trace level: simultaneous determination of lead and thallium, and bismuth and antimony

Pairs of elements with very small differences in their half-wave potentials were determined at trace levels by second harmonic a.c. anodic stripping voltammetry. The simultaneous determination of lead and thallium as well as that of bismuth and antimony in 1M hydrochloric acid as supporting electrolyte was found to be possible in the range of concentration ratios: 7:1 > or = C(Pb):C(Tl) > or = 1:36 and 45:1 > or = C(Sb):C(Bi) > or = 1:35, with <5 % relative error due to mutual interference. The limit of detection was approximately 10(-8)M for all four elements, and the precision and error were 2-3%. The simultaneous determination of these metals in mixtures with concentration ratios outside the quoted ranges is still feasible by the standard-addition technique.     

A study of Nafion-coated bismuth-film electrodes for the determination of trace metals by anodic stripping voltammetry

This work reports on the fabrication, characterization and applications of Nafion-coated bismuth-film electrodes (NCBFE's) for the determination of trace metals by anodic stripping voltammetry (ASV). A NCBFE was typically prepared by first applying a 5 microl drop of a 1% Nafion solution onto the surface of a glassy-carbon rotating-disk electrode. After evaporation of the solvent, the Bi film was plated on the electrode in situ(i.e. by spiking the sample with 1000 microg l(-1) of Bi(iii) and simultaneous electrolytic deposition of the metal ions and bismuth film on the electrode surface at -1.4 V) or ex-situ(i.e. by electrolytic deposition of the bismuth film in a separate solution containing 1000 microg l(-1) of Bi(iii), followed by the ASV measurement step in the sample solution). Various fabrication and operational parameters were thoroughly investigated and discussed in terms of their effect on the ASV signals. It was found that this voltammetric sensor was suitable for the determination of metals at trace levels by square-wave ASV (SWASV) due to its multi-element detection potential, improved analytical sensitivity, high resistance to surfactants, low cost, ease of fabrication, robustness, speed of analysis and low toxicity (as compared to traditional mercury electrodes). In the presence of 4 mg l(-1) of Triton X-100, the NCBFE afforded a 10-fold peak height enhancement for the Pb peak and a 14-fold enhancement for the Cd peak over a bare BFE while the determination of Zn was feasible only on the NCBFE. The limits of detection (at a signal-to-noise ratio of 3) were 0.1 microg l(-1) for Cd and Pb and 0.4 microg l(-1) for Zn for a deposition time of 10 min. Finally, the electrode was applied to different real samples (tap-water, urine and wine) for the analysis of trace metals with satisfactory results.     

Novel disposable bismuth-sputtered electrodes for the determination of trace metals by stripping voltammetry

This work describes a novel type of bismuth electrode for stripping voltammetry based on coating a silicon substrate with a thin bismuth film by means of sputtering. The bismuth-based sensors were characterized by optical methods (scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD)) and as well as by linear sweep voltammetry. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II), Pb(II) and Ni(II)) by stripping voltammetry. Well-formed stripping peaks were observed for trace concentrations of the target analytes demonstrating “proof-of-principle” for these sensors. This type of electrochemical device, utilizing thin-film technology for the formation of the bismuth film, holds promise for future applications in trace metal analysis.     

Determination of trace metals by anodic stripping voltammetry using a bismuth-modified carbon nanotube electrode

A bismuth-modified carbon nanotube electrode (Bi-CNT electrode) was employed for the determination of trace lead, cadmium and zinc. Bismuth film was prepared by in situ plating of bismuth onto the screen-printed CNT electrode. Operational parameters such as preconcentration potential, bismuth concentration, preconcentration time and rotation speed during preconcentration were optimized for the purpose of determining trace metals in 0.1M acetate buffer solution (pH 4.5). The simultaneous determination of lead, cadmium and zinc was performed by square wave anodic stripping voltammetry. The Bi-CNT electrode presented well-defined, reproducible and sharp stripping signals. The peak current response increased linearly with the metal concentration in a range of 2-100 microg/L. The limit of detection was 1.3 microg/L for lead, 0.7 microg/L for cadmium and 12 microg/L for zinc (S/N=3). The Bi-CNT electrode was successfully applicable to analysis of trace metals in real environments.     

Modification of carbon screen-printed electrodes by adsorption of chemically synthesized Bi nanoparticles for the voltammetric stripping detection of Zn(II), Cd(II) and Pb(II)

A simple procedure for the chemical synthesis of bismuth nanoparticles and subsequent adsorption on commercial screen-printed carbon electrodes offer reliable quantitation of trace zinc, cadmium and lead by anodic stripping square-wave voltammetry in nondeareated water samples. The influence of two hydrodynamic configurations (convective cell and flow cell) and the effect of various experimental variables upon the stripping signals at the bismuth-coated sensor are explored. The square-wave peak current signal is linear over the low ng mL⁻¹ range (120 s deposition), with detections limits ranging from 0.9 to 4.9 ng mL⁻¹ and good precision. Applicability to waste water certified reference material and drinking water samples is demonstrated. The attractive behaviour of the new disposable Bi nanoparticles modified carbon strip electrodes, coupled with the negligible toxicity of bismuth, hold great promise for decentralized heavy metal testing in environmental and industrial effluents waters.     

Disposable Bismuth Oxide Screen Printed Electrodes for the High Throughput Screening of Heavy Metals

We present a simplified approach for the trace screening of toxic heavy metals utilizing bismuth oxide screen printed electrodes. The use of bismuth oxide instead of toxic mercury films facilitates the reliable sensing of lead(II), cadmium(II) and zinc(II). A linear range over 5 to 150 μg L^?1 with detection limits of 2.5 and 5 μg L^?1 are readily observed for cadmium and lead in 0.1 M HCl, respectively. Conducting a simultaneous multi‐elemental voltammetric detection of zinc, cadmium and lead in a higher pH medium (0.1 M sodium acetate solution) exhibited a linear range between 10 and 150 μg L^?1 with detection limits of 5, 10 and 30 μg L^?1 for cadmium, lead and zinc respectively. The sensor is greatly simplified over those recently reported such as bismuth nanoparticle modified electrodes and bismuth film coated screen printed electrodes. The scope of applications of this sensor with the inherent advances in electroanalysis coupled with the negliable toxicity of bismuth is extensive allowing high throughput electroanalysis.     

A Study on Operational Parameters for Advanced Use of Bismuth Film Electrode in Anodic Stripping Voltammetry

A study is presented on the characterization, evaluation and optimization of several key operational parameters for a reliable and effective use of a bismuth film electrode (BiFE) as an advanced replacement of the mercury film electrode in anodic stripping voltammetric measurements of trace heavy metals. Applying in situ preparation of the BiFE and employing lead(II) and cadmium(II) as model analyte ions, key parameters including bismuth precursor salt and substrate surface (platinum, gold, glassy carbon, carbon paste, carbon fiber) for bismuth plating, concentration as well as cationic and anionic composition of the measurement solution, solution pH and temperature, potential interferents, and stripping modes were carefully examined for their effects in the preconcentration and stripping steps. Parameters such as substrate surface (except platinum), precursor salt, solution matrix and temperature showed no or little impact on the BiFE performance in stripping analysis. On the other hand, the BiFE performance was found to be dependent on the solution pH (with maximum efficiency in the range of 4 to 5), on the stripping mode (with square‐wave voltammetry as the best choice) and to a certain degree on the presence of surface active substances. The results revealed that the non‐toxic solid‐state BiFE is applicable under a wide variety of conditions which proves it highly suitable for practical work in environmental trace heavy metal analysis.     

Bismuth Film Microelectrode Modified with Overoxidized Poly‐1‐Naphtylamine Protective Membrane for Enhanced Stripping Voltammetric Detection

The application of protective overoxidized poly‐1‐naphtylamine membrane (ONAP) is demonstrated in combination with bismuth film microelectrode (ONAP‐BiFME) for anodic stripping voltammetric measurement of trace heavy metals in the presence of some selected surfactants. The ONAP membrane was electrochemically deposited on the surface of bare single carbon fiber microelectrode followed by the in situ or ex situ preparation of the bismuth film. The key operational parameters influencing the stripping performance of the ONAP‐BiFME were optimized and its electroanalytical performance was examined in the model solution containing Cd(II) and Pb(II) as test metal ions. The ONAP‐BiFME exhibited significantly enhanced stripping voltammetric response (approximately 70% for Cd(II) and 45% for Pb(II)) in comparison with unmodified BiFME in the absence of surfactants. In the presence of high concentrations, e.g., 20 mg L^?1, of anionic or cationic surfactants, the stripping signal for, e.g., Cd(II) decreased for less than 6% at the ONAP‐BiFME, whereas at the unmodified BiFME the signal attenuated considerably (approximately 38%). Moreover, in the presence of 10 mg L^?1 of nonionic surfactant Triton X‐100, the stripping signals at the bare BiFME were almost completely suppressed, whereas at the ONAP‐BiFME exhibited linear concentration behavior in the examined concentration range from 10 to 120 μg L^?1, with the calculated limit of detection of 5.0 μg L^?1 and 3.4 μg L^?1 for Cd(II) and Pb(II), respectively in connection with 60 s accumulation time. The attractive behavior of ONAP‐modified BiFME expands the applicability of bismuth‐based electrodes for measurement of trace heavy metals in real environments, where the presence of more complex matrix can be expected.     

Rational syntheses, structure, and properties of the first bismuth(II) carboxylate

Bismuth(II) trifluoroacetate (1), the first inorganic salt of bismuth in oxidation state +2, has been obtained in its pure, unstabilized form. Several synthetic routes suggested for the isolation of the new compound include (i) mild oxidation of elemental bismuth with some metal trifluoroacetates, e.g., Ag(I) and Hg(II); (ii) mild reduction of bismuth(III) trifluoroacetate with metals, such as Zn; (iii) comproportionation reaction between Bi and Bi(O(2)CCF(3))(3). The last approach gives the title compound 1 in quantitative yield as a sole product. Bismuth(II) trifluoroacetate has been characterized by NMR, IR, and UV-vis spectroscopy as well as by single-crystal X-ray diffraction. Crystallographic study reveals the dinuclear paddle-wheel structure for diamagnetic molecules Bi(2)(O(2)CCF(3))(4). The Bi-Bi bond distances in dimetal units of 1 are averaged to 2.9462(3) A, and there are no axial intermolecular contacts between these units in the solid state. The compound is volatile and exists in vapor phase up to 220 degrees C when it disproportionates back to Bi(0) and Bi(III) species, i.e., by the reverse of the synthetic route iii. In contrast, the solution chemistry is quite limited: the bismuth(II) trifluoroacetate is decomposed by the majority of common solvents, but it can be stabilized by aromatic systems. The dibismuth unit has been shown to be preserved in the latter solvents and can be crystallized out in a form of pi-adducts with arenes. Two such adducts, Bi(2)(O(2)CCF(3))(4).(C(6)H(5)Me) (2) and Bi(2)(O(2)CCF(3))(4).(1,4-C(6)H(4)Me(2))(2) (3), have been isolated as single crystals and characterized by X-ray diffraction techniques. In the structures of both 2 and 3, the bismuth(II) centers exhibit weak eta(6)-coordination to aromatic rings.     

复合铋膜电极阳极溶出法测定水样中的痕量铟

在玻碳电极上采用电化学沉积法制备了新型铕离子掺杂普鲁士蓝复合铋膜电极,建立了用示差脉冲阳极溶出法测定环境水样中痕量铟的分析方法。讨论了铟在常规铋膜电极和复合铋膜电极上的溶出性能,对铋膜的厚度、支持电解质、测定底液的pH、富集时间和富集电位等参数进行了优化。在最佳实验条件下,铟的阳极溶出峰电流与其浓度在2~20μg/L和20~100μg/L范围内分别呈良好的线性关系,检测下限为0.15μg/L(S/N=3),相对标准偏差RSD2.0%。该法用于实际水样中痕量铟的测定,样品回收率为97.5%~103%。