Bismuth Film Voltammetric Sensor on Pyrolyzed Photoresist/Alumina Support for Determination of Heavy Metals

Voltammetric sensors based on bismuth film electrodes are an attractive alternative to other sensors for application in electroanalysis of heavy metals. Bismuth film electrodes can be formed by a similar method on the same substrates as mercury. These systems were used most frequently for simultaneous determination of heavy metals such as Pb, Cd and Zn by anodic stripping voltammetry. Our voltammetric sensor was fabricated on an alumina substrate. A photoresist film prepared by pyrolysis of positive photoresist S‐1813 SP15 on the alumina substrate was used as an electrode support for bismuth film deposition. The influence of the Nafion membrane on the measurement sensitivity of the sensor and mechanical stability of the bismuth film were investigated. The sensor was successfully applied for determination of Pb, Cd and Zn in an aqueous solution in the concentration range of 0.2 to 10 µg L^?1 by square wave anodic stripping voltammetry on an in‐situ formed bismuth film electrode with Nafion‐coating. Parameters of the sensor such as sensitivity, linearity, detection limit, repeatability and life‐time were evaluated. In the best case, the detection limits were estimated as 0.07, 0.11 and 0.63 µg L^?1 for Pb, Cd and Zn, respectively. Finally, the applicability of the sensor was tested in analysis of Pb, Cd and Zn in real samples of tap and river water using the method of standard additions.     

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.     

Voltammetric Determination of Pb(II) and Cd(II) Ions in Well Water Using a Sputtered Bismuth Screen‐Printed Electrode

A method using commercially available sputtered bismuth screen‐printed electrodes (Bi_spSPE), as substitute to mercury electrodes, for the determination of trace Pb(II) and Cd(II) ions in drinking well water samples collected in a contaminated area in The Republic of El Salvador by means of differential pulse anodic stripping voltammetry (DPASV) has been proposed. The comparable detection and quantification limits obtained for both Bi_spSPE and hanging mercury drop electrode (HMDE), together with the similar results with a high reproducibility obtained in these water samples analyses recommend the applicability of Bi_spSPE for the determination of low level of metal concentrations in natural samples.     

Bismuth film electrode for anodic stripping voltammetric determination of tin

The bismuth film electrode (BiFE), in combination with anodic stripping voltammetry, offers convenient measurement of low concentrations of tin. The procedure involves simultaneous in situ formation of the bismuth film electrode on a glassy carbon substrate electrode, together with electrochemical deposition of tin, in a non-deaerated model solution containing bismuth ions, catechol as complexing agent and the metal analyte, followed by an anodic stripping scan. The BiFE is characterized by an attractive electroanalytical performance, with two distinct voltammetric stripping signals corresponding to tin, accompanied with low background contributions. Several experimental parameters were optimized, such as concentration of bismuth ions and catechol, deposition potential, deposition time and pH of the model solution. In addition, a critical comparison is given with bare glassy carbon and mercury film electrodes, revealing the superior characteristics of BiFE for measurement of tin. BiFE exhibited highly linear behavior in the examined concentration range from 1 to 100 μg L⁻¹ of tin (R² = 0.997), an LoD of 0.26 μg L⁻¹ tin, and good reproducibility with a calculated R.S.D. of 7.3% for 10 μg L⁻¹ tin (n = 10). As an example, the practical applicability of BiFE was tested with the measurement of tin in a real sample of seawater.     

Electrochemical Properties and Range of Application of Mixed Gold Bismuth Electrodes

Electrochemical properties for mixed gold‐bismuth electrodes have been evaluated. Increased overpotential towards the hydrogen evolution reaction (HER) was found as a function of increased bismuth content in the gold‐bismuth mixture. Compared to a bare gold electrode, the overvoltage was increased by 80 mV for gold with 2% bismuth added (AuBi2), 170 mV for 6% bismuth added (AuBi6), and 580 mV for 25% bismuth added (AuBi25). Cyclic voltammetry (CV) in a NaOH solution was also carried out to study the formation of different oxide products on the surface. The practical use of such electrodes was demonstrated by differential pulse anodic stripping voltammetry (DPASV) for the detection of copper and mercury, and good linearity was found even for concentrations down to 0.25 μg/L. In addition to stability tests in NH₄Cl, the analytical use and stability over time were evaluated in purified scrubbing water and polluted river water.     

Simultaneous and Sensitive Detection of Cd(II) and Pb(II) Using a Novel Bismuth Film/Ordered Mesoporous Carbon‐molecular Wire Modified Graphite Carbon Paste Electrode

An electrochemical sensor for the simultaneous and sensitive detection of Cd(II) and Pb(II) is proposed on the basis of square‐wave anodic stripping voltammetry (SWASV) experiments using a novel bismuth film/ordered mesoporous carbon‐molecular wire modified graphite carbon paste electrode (Bi/OMC‐MW/GCPE). Ordered mesoporous carbon (OMC) and molecular wire (MW) (diphenylacetylene) were used as the modifier and binder, respectively. The Bi/OMC‐MW/GCPE was prepared with the addition of graphite powder, OMC and DPA at the ratio of 2 : 1 : 1. The electrochemical properties and morphology of the electrode were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), SWASV and scanning electron microscopy (SEM). The parameters affecting the stripping current response were investigated and optimized. The experimental results show that the prepared electrode exhibited excellent electrochemical performance, good electrical conductivity and a high stripping voltammetric response. Under optimized conditions, a linear range was achieved over a concentration range from 1.0 to 70.0 μg/L for both Cd(II) and Pb(II) metal ions, with detection limits of 0.07 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N=3) with the deposition time 150 s. Moreover, the sensor exhibited improved sensitivity and reproducibility compared to traditional CPEs. The fabricated electrode was then successfully used to satisfactorily detect Cd(II) and Pb(II) in real soil samples.     

Anodic behaviour of the (222) macrobicyclic ligand on mercury electrode in propylenecarbonate

The anodic behaviour of the free macrobicyclic ligand (222) was examined by various electrochemical techniques on mercury and on platinum electrodes. From results on platinum electrode using cyclic voltammetry it appears that the anodic oxidation of (222) proceeds irreversibly at potentials more positive than +0.7 V (aq. SCE), however, its mechanism could not be determined because the anodic signal was not well developed. Under polarographic conditions a reversible anodic diffusion controlled wave at E_1/2=+0.08 V (aq. SCE) was observed, corresponding to a complex formation of the ligand (222) with the ions of mercury formed by anodic polarization of mercury electrode. In excess of mercuric cations a cathodic wave at slightly more positive potentals was found.     

Determination of Lead(II) Using Screen‐Printed Bismuth‐Antimony Film Electrode

This work presents a disposable bismuth‐antimony film electrode fabricated on screen‐printed electrode (SPE) substrates for lead(II) determination. This bismuth‐antimony film screen‐printed electrode (Bi‐SbSPE) is simply prepared by simultaneously in situ depositing bismuth(III) and antimony(III) with analytes on the homemade SPE. The Bi‐SbSPE can provide an enhanced electrochemical stripping signal for lead(II) compared to bismuth film screen‐printed electrodes (BiSPE), antimony film screen‐printed electrodes (SbSPE) and bismuth‐antimony film glassy carbon electrodes (Bi‐SbGC). Under optimized conditions, the Bi‐SbSPE exhibits attractive linear responses towards lead(II) with a detection limit of 0.07 µg/L. The Bi‐SbSPE has been demonstrated successfully to detect lead in river water sample.     

预镀铋膜阳极溶出伏安法测定废水中微量铅和镉

本文采用预镀铋膜法修饰玻碳电极,并用该电极对废水中微量铅和镉同时进行了阳极溶出伏安法测定,研究了预镀铋膜测定铅和镉的条件。实验结果表明:铅和镉在铋膜电极上可得到灵敏的电位溶出峰,峰高和溶出电位与汞膜电极法相近,使用预镀铋膜电极可避免使用汞电极带来的环境污染。     

Underpotential Deposition Study and Determination of Bismuth on Gold Electrode by Using Voltammetry

ＴｈｅｃｏｍｂｉｎａｔｉｏｎｏｆｓｔｒｉｐｐｉｎｇｖｏｌｔａｍｍｅｔｒｙｗｉｔｈＵＰＤｃａｎｌｅａｄｔｏｔｈｅｉｍｐｒｏｖｅｍｅｎｔｏｆｓｅｎｓｉｔｉｖｉｔｙ ,ｓｅｌｅｃｔｉｖｉ ｔｙａｎｄｒｅｖｅｒｓｉｂｉｌｉｔｙｆｏｒｅｌｅｃｔｒｏａｎａｌｙｔｉｃａｌｐｕｒｐｏｓｅａｎｄａｖｏｉｄｔｈｅｕｓｅｏｆｔｏｘｉｃｍｅｒｃｕｒｙａｓｔｈｅｗｏｒｋｅｌｅｃｔｒｏｄｅ1ａｎｄｔｈｅｎａｎａｌｙｔｉｃａｌａｐｐｌｉｃａｔｉｏｎｓｈａｖｅｂｅｅｎｄｅｓｃｒｉｂｅｄ .2 4 Ｉｎｔｈｉｓｗｏｒｋ ,ｗｅｄｅｖｅｌｏ…     

Evaluation of Bismuth Modified Carbon Thread Electrode for Simultaneous and Highly Sensitive Cd (II) and Pb (II) Determination

Bismuth film modified and chemically activated carbon micro‐thread electrodes were investigated for the simultaneous determination of Cd(II) and Pb(II) using square wave anodic stripping voltammetry. The carbon thread electrode was characterised using both surface and electrochemical techniques. Electrochemical impedance spectroscopy (EIS) studies demonstrated that the H₂SO₄/IPA‐treated carbon thread electrode showed a much improved resistance response (R_ct=23 Ω) compared to the IPA‐untreated carbon thread (R_ct=8317 Ω). Furthermore, parameters such as the effect of deposition potential, deposition time and Bi(III) concentration were explored using square wave voltammetry. Detection limits (S/N=3) for Cd(II) and Pb(II) were found to be 1.08 µg L^?1 and 0.87 µg L^?1, respectively and response was found to be linear over the range 5–110 µg L^?1. The proposed Bi/IPA‐treated carbon thread electrode exhibited a high selectivity towards Cd(II) and Pb(II) even in the presence of a range of heavy metals and is capable of repetitive and reproducible measurements, being attributed to the high surface area, geometry and electrode treatment characteristics. The proposed metal ion sensor was employed to determine cadmium and lead in river water samples and % RSD was found to be 5.46 % and 5.93 % for Cd(II) and Pb(II) respectively (n=3). Such facile sensing components favour the development of cost effective portable devices for environmental sample analysis and electrochemical applications.     

Coal as a New Carbon Paste Electrode Modifier with Sorption Properties

A new type of carbon paste electrode modified with subbituminous and bituminous coal is presented. The operability of the coal carbon paste electrode with respect to the working potential window attainable was tested in various electrolytes. Cyclic voltammetry of the reference redox system [Fe(CN)₆]^3?/4? was performed to evaluate electron transfer kinetics. Open‐circuit sorption of Cd(II), Pb(II), and Cu(II) with subsequent anodic stripping voltammetry was used to pilot coal sorption ability. The coal modified carbon paste electrode was also examined as a support for mercury film deposition and anodic stripping voltammetry of metals.     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Functioning of antimony film electrode in acid media under cyclic and anodic stripping voltammetry conditions

New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of in situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. Five different carbon- and metal-based substrate transducer electrodes revealed a clear advantage of the former ones while the concentration of the precursor Sb(III) ion exhibited a distinct influence on the ASV functioning of the SbFE. Among six acids examined as potential supporting electrolytes the HNO₃ was demonstrated to yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO₃ is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. By carrying out a systematic CV and ASV investigation using a medium exchange protocol, we confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Finally, the practical analytical application of the proposed ASV method was successfully tested and evaluated by measuring the three metal analytes in ground (tap) and surface (river) water samples acidified with HNO₃. Our results approved the appropriateness of the SbFE and the proposed method for measuring low μg L⁻¹ levels of some toxic metals, particularly taking into account the possibility of on-field testing and the use of low cost instrumentation.     

Ex Situ Scanning Electrochemical Microscopy (SECM) Investigation of Bismuth‐ and Bismuth/Lead Alloy Film‐Modified Gold Electrodes in Alkaline Medium

Scanning electrochemical microscopy (SECM) in feedback mode was employed to characterise the reactivity and microscopic peculiarities of bismuth and bismuth/lead alloys plated onto gold disk substrates in 0.1 mol L^?1 NaOH solutions. Methyl viologen was used as redox mediator, while a platinum microelectrode was employed as the SECM tip. The metal films were electrodeposited ex situ from NaOH solutions containing either bismuth ions only or both bismuth and lead ions. Approach curves and SECM images indicated that the metal films were conductive and locally reactive with oxygen to provide Bi³⁺ and Pb²⁺ ions. The occurrence of the latter chemical reactions was verified by local anodic stripping voltammetry (ASV) at the substrate solution interface by using a mercury‐coated platinum SECM tip. The latter types of measurements allowed also verifying that lead was not uniformly distributed onto the bismuth film electrode substrate. These findings were confirmed by scanning electron microscopy images. The surface heterogeneity produced during the metal deposition process, however, did not affect the analytical performance of the bismuth coated gold electrode in anodic stripping voltammetry for the determination of lead in alkaline media, even in aerated aqueous solutions. Under the latter conditions, stripping peak currents proportional to lead concentration with a satisfactory reproducibility (within 5 % RSD) were obtained.     

Electrochemical Impedance Characterization of Nafion‐Coated Carbon Film Resistor Electrodes for Electroanalysis

Carbon film disk electrodes with Nafion coatings have been characterized by electrochemical impedance spectroscopy (EIS) with a view to a better understanding of their advantages and limitations in electroanalysis, particularly in anodic stripping voltammetry of metal ions. After initial examination by cyclic voltammetry, spectra were recorded over the full potential range in acetate buffer solution at the bare electrodes, electrodes electrochemically pretreated in acid solution, and Nafion‐coated pretreated electrodes in the presence and absence of dissolved oxygen. EIS equivalent circuit analysis clearly demonstrated the changes between these electrode assemblies. In order to simulate anodic stripping voltammetry conditions, spectra were also obtained in the presence of cadmium and lead ions in solution at Nafion‐coated electrodes, both after metal ion deposition and following re‐oxidation. Permanent changes to the structure of the Nafion film occurred, which has implications for use of these electrode assemblies in anodic stripping voltammetry at relatively high trace metal ion concentrations.     

聚苯胺颗粒电极的制备与其电化学行为

采用循环伏安法,以含苯胺(An)的硫酸溶液为电解质,采用循环伏安技术在Pt微盘电极上得到随机、不连续沉积的聚苯胺(PAn)微颗粒和PAn膜.实验结果表明:H2SO4浓度、苯胺浓度、电位扫描上限和扫速对电化学合成随机、不连续沉积的PAn微颗粒具有重要影响.不连续随机沉积的PAn微颗粒电极与PAn膜电极在锂离子(Li-ion)电池电解质溶液中的行为有明显差异,不连续随机沉积的PAn微颗粒电极可以清楚地得到氧化还原电流峰,而PAn膜电极无法形成清晰的氧化还原电流峰.采用较缓慢扫描速度更有利于形成良好"结晶"的不连续PAn颗粒电极,该种电极可以同时具有高比能量和可逆性能.     

Determination of Trace Tl(I) by Anodic Stripping Voltammetry on Novel Disposable Microfabricated Bismuth‐Film Sensors

This work reports the trace determination of Tl(I) by square‐wave anodic stripping voltammetry (SWASV) on novel microsensors equipped with a bismuth‐film electrode (BiFE). The sensors were fabricated by a multistep microfabrication approach combining sputtering (to deposit the electrode materialm, bismuth‐ and the insulator SiO₂, on the surface of a silicon wafer) and photolithography (to define the geometry of the sensor). The effect of the preconcentration time, the preconcentration potential and the SW stripping parameters were investigated. Using the selected conditions, the 3σ limit of detection was 0.6 µg L^?1 of Tl(I) at a preconcentration time of 240 s and the percent relative standard deviation was 4.3 % at the 10 µg L^?1 level (n=8). In order to eliminate the interference caused by Pb(II) and Cd(II), EDTA was added in the sample solution The method was successfully applied to the determination of Tl(I) in a certified lake water sample. These new sensors exhibit excellent mechanical stability and offer wide scope as mercury‐free disposable sensors for trace metal analysis.     

Voltammetric Determination of Neonicotinoid Pesticides at Disposable Screen‐Printed Sensors Featuring a Sputtered Bismuth Electrode

This work reports the determination of 5 neonicotinoid pesticides (Clothianidin, Imidacloprid, Thiamethoxam, Nitenpyram and Dinotefuran) in water samples by cathodic differential pulse (DP) voltammetry at screen‐printed disposable sensors featuring a sputtered bismuth thick‐film working electrode, a Ag reference electrode and a carbon counter electrode. The performance of the bismuth thick‐film electrodes was compared to that of a home‐made bismuth thin‐film electrode and a bismuth‐bulk electrode. The electrodes were further characterized by electrochemical and optical techniques. The effect of the pH of the supporting electrolyte on the DP reduction currents of the 5 pesticides was studied. The limits of quantification (LOQs) in 4 water matrices (distilled water, tap water, mineral water and surface water) were in the range 0.76 to 2.10 mg L^?1 but severe matrix effects were observed in the analysis of mineral and, especially, surface water samples. Using a solid‐phase extraction (SPE) procedure using Lichrolut EN cartridges and elution with methanol, the matrix effects were substantially reduced and the LOQs were in the range 9 to 17 µg L^?1_. The recoveries of surface water samples spiked with the 5 target neonicotinoids at two concentration levels (20 and 50 µg L^?1) were in the range 89 to 109 % and the % relative standard deviations ranged from 4.3 to 7.2 %.