Nafion/Poly(sodium 4‐styrenesulfonate) Mixed Coating Modified Bismuth Film Electrode for the Determination of Trace Metals by Anodic Stripping Voltammetry

To improve the reproducibility, stability, and sensitivity of bismuth film electrode (BiFE), we studied the performances of a mixed coating of two cation‐exchange polymers, Nafion (NA) and poly(sodium 4‐styrenesulfonate) (PSS), modified glassy carbon BiFE (GC/NA‐PSS/BiFE). The characteristics of GC/NA‐PSS/BiFE were investigated by scanning electron microscopy and cyclic voltammetry. Various parameters were studied in terms of their effect on the anodic stripping voltammetry (ASV) signals. Under optimized conditions, the limits of detection were 71 ng L^?1 for Cd(II) and 93 ng L^?1 for Pb(II) with a 10 min preconcentration. The results exhibited that GC/NA‐PSS/BiFE can be a reproducible and robust tool for monitor of trace metals by ASV rapidly and environmentally friendly, even in the presence of surface‐active compounds.     

A Study of Nafion‐Coated Bismuth‐Film Electrode for the Determination of Zinc,Lead, and Cadmium in Blood Samples

In this article a sensitive differential pulse stripping voltammetry technique on Nafion‐coated bismuth‐film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L^?1 for Cd(II), 0.13 μg L^?1 for Pb(II), and 0.97 μg L^?1 for Zn(II) respectively.     

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.     

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.     

Determination of trace Pb(Ⅱ), Cd(Ⅱ) and Zn(Ⅱ) using differential pulse stripping voltammetry without Hg modification

In this work,we reported a simultaneous determination approach for Pb(II),Cd(II)and Zn(II)atμg L 1concentration levels using differential pulse stripping voltammetry on a bismuth film electrode(BiFE).The BiFE could be prepared in situ when the sample solution contained a suitable amount of Bi(NO)3,and its analytical performance was evaluated for the simultaneous determination of Pb(II),Cd(II)and Zn(II)in solutions.The determination limits were found to be 0.19μg L 1for Zn(II),and0.28μg L 1for Pb(II)and Cd(II),with a preconcentration time of 300 s.The BiFE approach was successfully applied to determine Pb(II),Cd(II)and Zn(II)in tea leaf and infusion samples,and the results were in agreement with those obtained using an atomic absorption spectrometry approach.Without Hg usage,the in situ preparation for BiFE supplied a green and acceptability sensitive method for the determination of the heavy metal ions.     

Properties of Poly(sodium 4‐styrenesulfonate)‐Ionic Liquid Composite Film and Its Application in the Determination of Trace Metals Combined with Bismuth Film Electrode

A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1‐butyl‐3‐methyl‐imidazolium hexafluorophosphate (BMIMPF₆) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4‐styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)₆^4?/Fe(CN)₆^3? can be effectively improved at the PSS‐BMIMPF₆ modified GC. The bismuth modified PSS‐BMIMPF₆ composite film electrodes (GC/PSS‐BMIMPF₆/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS‐BMIMPF₆/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50 μg L^?1. And the detection limits were 0.07 μg L^?1 for Cd(II) and 0.09 μg L^?1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120 s, respectively. Finally, the GC/PSS‐BMIMPF₆/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy.     

Anodic Stripping Voltammetry Combined with Sequential Injection Analysis for Measurements of Trace Metal Ions with Bismuth‐ and Antimony Film Electrodes under Comparable Conditions

Anodic stripping voltammetry combined with sequential injection analysis (ASV‐SIA) was selected to examine the use of bismuth‐ and antimony‐film plated glassy carbon electrodes under comparable conditions for the determination of Pb(II) and Cd(II) ions. Of interest were the conditions for film deposition, as well as the composition of sample/carrier solutions, including concentrations of Sb(III) or Bi(III) and HCl. Then, by the optimized procedure, one could determine Pb(II), Cd(II), and Zn(II) ions at the low µg L^?1 level and ASV‐SIA configuration with both electrodes tested on analysis of a water sample.     

Tellurium Film Electrodes Deposited on Carbon and Mesoporous Carbon Screen‐printed Substrates for Anodic Stripping Voltammetric Determination of Copper

The performance of screen‐printed electrodes modified in situ with tellurium film for the anodic stripping voltammetric (ASV) determination of Cu(II) is reported. It was found that two types of screen‐printed substrates, namely carbon and mesoporous carbon, were optimal for this application. The selected in situ tellurium film modified electrodes were applied for the square wave ASV determination of copper at μg L⁻¹ concentration levels. Well‐defined and reproducible Cu oxidation stripping peaks were produced at a potential more negative than the anodic dissolution of tellurium. The highest sensitivity of Cu determination was achieved in 0.05 M HCl containing 50 μg L⁻¹ Te(IV) after 300 s of accumulation at −0.5 V. Using the optimized procedure, a linear range from 2 to 35 μg L⁻¹ of Cu(II) was obtained with a detection limit of 0.5 μg L⁻¹ Cu(II) (S/N=3) for 300 s of deposition time. Both sensors, carbon TeF‐SPE and mesoporous carbon TeF‐SPE, were successfully applied for the quantification of Cu in a certified reference surface water sample.     

Performance of Ex Situ Bismuth Film Rotating Disk Electrode in Trace Metal Analysis by Stripping Chronopotentiometry: Definition of the Depletion Regime and Optimization of Experimental Parameters

The potentiality of the ex situ deposited bismuth film electrode, allied to the rotation of a glassy carbon disk electrode (BiFE‐RDE), was exploited in trace metal analyses of lead(II) and cadmium(II) by stripping chronopotentiometry (SCP). A single BiFE (6.2 nm film thickness) can be used for a 1‐day term with no significant variation in the analytical signal. The limit of detection (3σ) for a deposition time of 40 s and an oxidation current of 15×10^?9 A was 1.5×10^?8 M for Pb(II) and 3.0×10^?8 M for Cd(II). BiFE‐RDE was successfully applied to the direct SCP determination of lead(II) in a fresh water certified material.     

Nafion‐Coated Bismuth Film Electrodes for the Determination of Trace Lead and Cadmium in Herbal Medicines by Anodic Stripping Voltammetry

A novel analytical procedure for the determination of Pb(II) and Cd(II) in herbal medicines by differential pulse anodic stripping voltammetry (DPASV) on Nafion‐coated bismuth film electrode (NCBFE) was proposed and experimentally validated. Various experimental parameters, which influenced the response of the NCBFE to these metals in real samples, were optimized. The results showed that there were well‐defined peaks of Pb and Cd in herb samples at deposition potential of ?1.2 V and deposition time of 300 s. The analytical performance of the NCBFE was evaluated in the presence of dissolved oxygen, with the determination limits of 0.35 µg·L^?1 for Pb and 0.72 µg·L^?1 for Cd and recoveries of 87.8% –105.4% for Pb and 89.5% –108.5% for Cd obtained from different samples. The Pb and Cd concentrations in the studied samples have been also determined by graphite furnace atomic absorption spectrometry (GFAAS), suggesting that there was a satisfactory agreement between the two techniques, with relative errors lower than 6.5% in all cases. The great advantages of the proposed method over the spectroscopic method were characterized by its simplicity, selectivity and short analysis time, simultaneous analysis of different metals and cost‐efficiency.     

A Simple and Sensitive Method for the Detection of Trace Pb(II) and Cd(II) based on Nafion‐coated Antimony Film Electrode

Nafion‐coated antimony film electrode (NCAFE) was prepared in situ by simultaneously plated antimony with analytes, and applied to the determination of trace Pb(II) and Cd(II) in non‐deaerated solutions by differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters, which influenced the response of the NCAFE to those metals, were thoroughly optimized and discussed. The results indicated that the sensitivity and resistance to surfactants at the NCAFE were remarkably improved with relative to the antimony film electrode (AFE). In the presence of 5 mg·L^?1 gelatin, the peak heights at the NCAFE showed 4‐fold enhancement for Pb and a 9‐fold enhancement for Cd over a bare AFE. Reproducibility of the sensor was satisfactory, and the relative standard deviations were 4.8% for 20 μg·L^?1 Pb and 3.2% for 25 μg·L^?1 Cd (n=15) with preconcentration time of 180 s. The determination limits (S/N=3) of this sensor were determined to be 0.15 μg·L^?1 for Pb and 0.30 μg·L^?1 for Cd with accumulation time of 300 s. The NCAFE was successfully applied to determining Pb(II) and Cd(II) in vegetable and water samples with satisfactory results.     

Sequential Voltammetric Determination of Uranium,Cadmium and Lead by Using the ex situ Bismuth Film Electrode: Application to Phosphate Fertilizers

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)‐cupferron complex in the differential pulse mode (detection limit of 1.0 µg L^?1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L^?1 for Cd (II) and 2.43 µg L^?1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO₃/H₂O₂). The following value ranges were evaluated: U (VI) 37.2–150 mg kg^?1, Pb (II) 78.3–204 mg kg^?1 and Cd (II) 44.1–71.6 mg kg^?1. Validation was performed by using the standard reference materials SRM‐695 – phosphate fertilizer – and SRM‐1643e – water.     

Sequential injection monosegmented flow voltammetric determination of cadmium and lead using a bismuth film working electrode

A cost-effective sequential injection monosegmented flow analysis (SI-MSFA) with anodic stripping voltammetric (ASV) detection has been developed for determination of Cd(II) and Pb(II). The bismuth film working electrode (BiFE) was employed for accumulative preconcentration of the metals by applying a fixed potential of −1.10 V versus Ag/AgCl electrode for 90 s. The SI-MSFA provides a convenient means for preparation of a homogeneous solution zone containing sample in an acetate buffer electrolyte solution and Bi(III) solution for in situ plating of BiFE, ready for ASV measurement at a flow through thin layer electrochemical cell. Under the optimum conditions, linear calibration graphs in range of 10-100 μg L⁻¹ of both Cd(II) and Pb(II) were obtained with detection limits of 1.4 and 6.9 μg L⁻¹ of Cd(II) and Pb(II), respectively. Relative standard deviations were 2.7 and 3.1%, for 11 replicate analyses of 25 μg L⁻¹ Cd(II) and 25 μg L⁻¹ Pb(II), respectively. A sample throughput of 12 h⁻¹ was achieved with low consumption of reagent and sample solutions. The system was successfully applied for analysis of water samples collected from a draining pond of zinc mining, validating by inductively coupled plasma-optical emission spectroscopy (ICP-OES) method.     

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).     

Ex Situ Prepared Antimony Film Electrode for Electrochemical Stripping Measurement of Heavy Metal Ions

The antimony film electrode (SbFE) was prepared ex situ for anodic and adsorptive stripping voltammetric measurement of selected heavy metal ions. The electrode revealed good linearity for Cd(II) and Pb(II) in a nondeaerated solution of 0.01 M HCl in the examined concentration range from 25 to 80 μg L^?1 with limits of detection of 1.1 μg L^?1 for Cd(II) and 0.3 μg L^?1 for Pb(II) and an excellent reproducibility. The preplated SbFE was also preliminary tested for measuring low levels of Ni(II) using adsorptive stripping voltammetry exhibiting good linearity and sensitivity in combination with only a 30 s deposition step.     

Bismuth‐Coated Iridium Microwire Electrode for the Determination of Trace Metals by Anodic Stripping Voltammetry

This work reports the utility of an iridium microwire plated in situ with a bismuth film for the simultaneous determination of Pb(II) and Cd(II) by square‐wave anodic stripping voltammetry (SWASV). The experimental variables (concentration of the bismuth plating solution, preconcentration potential, accumulation time) were investigated. The limit of detection was 1 µg L^?1 for Pb(II) and 1.5 µg L^?1 for Cd(II) (at 300 s of preconcentration) and the % relative standard deviations were lower than 4.9 % and 5.5 %, respectively, at the 20 µg L^?1 level (n=8). In addition, a study was made of coating the iridium‐based bismuth‐film microsensor with a film of Nafion for operation in the presence of surfactants. Finally, the electrode was applied to the determination of Pb(II) and Cd(II) in wastewater and tapwater samples.     

Voltammetric Behavior of Testosterone on Bismuth Film Electrode: Highly Sensitive Determination in Pharmaceuticals and Human Urine by Square‐Wave Adsorptive Stripping Voltammetry

In this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L^?1 testosterone in Britton? Robinson buffer, pH 5.0 containing 3 mmol L^?1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L^?1 (0.09 ng mL^?1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.     

Adsorptive Stripping Voltammetric Determination of Trace Uranium with a Bismuth‐Film Electrode Based on the U(VI)→U(V) Reduction Step of the Uranium‐Cupferron Complex

This work reports the use of adsorptive stripping voltammetry (AdSV) for the determination of uranium on a preplated rotating‐disk bismuth‐film electrode (BiFE). The principle of the method relied on the complexation of U(VI) ions with cupferron and the subsequent adsorptive accumulation of the complex on the surface of the BiFE. The uranium in the accumulated complex was then reduced by means of a cathodic voltammetric scan while the analytically useful U(VI)→U(V) reduction signal was monitored. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3σ limit of detection for uranium was 0.1 μg L^?1 at a preconcentration time of 480 s and the relative standard deviation was 4.7% at the 5 μg L^?1 level for a preconcentration time of 120 s (n=8). The accuracy of the method was established by analyzing a reference sea water sample.     

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.     

Stripping Chronopotentiometry and Stripping Voltammetry of Mixtures of Heavy Metal Ions Producing Close Signals: The Cd(II)‐Pb(II)‐Phthalate System

The effects of the proximity of the signals of two heavy metal ions in stripping voltammetry (SV) and constant‐current stripping chronopotentiometry (SCP) is studied at mercury drop (HMDE) and mercury film (MFE) electrodes. For this purpose, the Cd(II)‐Pb(II)‐phthalate system is used, taking advantage of the approaching of the signals corresponding to Cd(II)‐phthalate and Pb(II)‐phthalate labile complexes as phthalate is added to mixtures of Cd(II) and Pb(II)‐ions. The results are compared with those obtained by differential pulse polarography (DPP) and by stripping measurements on the Pb(II)‐phthalate system alone, showing discrepancies in SCP data under nondepletive conditions and negligible differences in the other cases.