Copper film electrode for anodic stripping voltammetric determination of trace mercury and lead

A novel in-situ prepared copper film electrode (CuFE) for anodic stripping voltammetric measurement of trace levels of Hg(II) and Pb(II) is presented. The optimal electroanalytical performance of the CuFE was achieved in electrolyte solution comprising 0.1 M HCl and 0.4 M NaCl. The CuFE exhibited excellent operation in the presence of dissolved oxygen with calculated LoD of 0.1 μg L^− 1 Hg(II) and 0.06 μg L^− 1 Pb(II) in combination with 300 s accumulation time, repeatability with RSD of 4.5% for Hg(II) and 0.9% for Pb(II) (n = 12), and favourable linear response in the examined concentration range of 10–100 μg L^− 1 (R² = 0.997) for Hg and 5–70 μg L^− 1 (R² = 0.999) for Pb after 120 s accumulation. The electrode enabled also simultaneous detection of both investigated metal ions and revealed promising electroanalytical characteristics similar to or in certain cases surpassing those of commonly used gold electrodes.     

Anodic stripping voltammetric determination of bismuth(III) using a Tosflex-coated mercury film electrode

A Tosflex-mercury film electrode (TMFE) was prepared by spin-coating a solution of the perfluorinated anion exchange polymer Tosflex onto a glassy carbon electrode surface followed by electrodeposition of mercury film on this electrode. This electrode was used for the determination of trace bismuth(III) which was preconcentrated onto the TMFE as anionic bismuth(III) complexes with chloride in a chloride medium. The preconcentration was carried out at a potential of-0.2 V, and the preconcentration of the bismuth(III) was enhanced significantly by the anion-exchange feature of Tosflex. The accumulated bismuth(III) was then determined by anodic square-wave stripping voltammetry (SWSV). Various parameters influencing the determination of bismuth(III) were examined in detail. With 2 min accumulation, the analytical signal versus concentration dependence was linear up to 50 ppb, and the detection limit was 0.58 ppb. This modified electrode showed good resistance to the interferences from surface-active compounds and common ions.     

Anodic stripping voltammetric determination of trace lead with a nafion/crown-ether film electrode

An electrode for the anodic stripping voltammetric determination of trace lead has been made by coating glassy carbon with a film of Naflon in which a crown ether is incorporated. The sensitivity is increased because of continuous transfer of lead from solution to the electrode surface by complexation with the crown ether and reduction during the deposition period. A detection limit of 5 x 10(-10)M has been obtained by electrodeposition for 3 min. The method is sensitive, simple and relatively rapid, with a relative standard deviation of 8% at the 2 x 10(-9)M level.     

Adsorptive stripping voltammetric determination of trace concentrations of molybdenum at an in situ plated lead film electrode

An in situ plated lead film electrode has been applied for adsorptive stripping voltammetric determination of trace concentrations of molybdenum in the presence of Alizarin S. The procedure is based on the preconcentration of the molybdenum-Alizarin S complex at an in situ plated lead film electrode held at −0.6 V (versus Ag/AgCl), followed by a negatively sweeping square wave voltammetric scan. The peak current is proportional to the concentration of molybdenum over the range 2 × 10⁻⁹ to 5 × 10⁻⁸ mol L⁻¹, with a 3σ detection limit of 9 × 10⁻¹⁰ mol L⁻¹ with an accumulation time of 60 s. The measurements were carried out from underaerated solutions. The proposed procedure was validated in the course of Mo(VI) determination in water certified reference materials.     

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L^–1 HCl solution containing 0.02 mol L^–1 KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at –0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about –0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I^– remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10^–10–5×10^–7 mol L^–1. The lowest detectable concentration of Hg²⁺ is 2×10^–10 mol L^–1 at 5 min accumulation. The relative standard deviation (RSD) at 1×10^–8 mol L^–1 Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.     

Ultra trace adsorptive stripping voltammetric determination of atrazine in soil and water using mercury film electrode

In situ mercury film electrode produced in the presence of thiocyanate has been shown extremely useful for highly sensitive adsorptive stripping voltammetric measurements of atrazine down to sub-μg L⁻¹ level. Operational parameters have been optimized and the stripping voltammetric performance has been investigated using square wave scans. The adsorptive stripping response is linear over the range of 0.5-60 μg L⁻¹ atrazine, with a detection limit of 0.024 μg L⁻¹. The method has been applied to the determination of atrazine in soil and water samples.     

Adsorptive stripping voltammetric determination of dimenhydrinate at a hanging mercury drop electrode

Dimenhydrinate exhibits a single adsorptive stripping peak at a hanging mercury drop electrode after accumulation at 0.0V vs Ag/AgCl electrode at pH 3.8 (acetate buffer). The addition of trace amounts of copper ions enhanced the dimenhydrinate peak and its height depends on the concentration of each dimenhydrinate and Cu²⁺. The adsorptive stripping response was evaluated with respect to accumulation time and potential, concentration dependence, electrolyte, the presence of other purines, surfactants and other metal ions, and some variables. The calibration graph for dimenhydrinate determination is linear over the range 2.0×10^–8–2.0×10^–7 M (pre-concentration for 60s). The correlation factor is found to be 0.985 and RSD is 3.2% at 1.0×10^–7 M. Detection limit is 1.0×10^–8 M after 5 min accumulation. The determination of dimenhydrinate in pharmaceutical formulations by the proposed method is also reported.     

Electromembrane extraction and anodic stripping voltammetric determination of mercury(II) using a glassy carbon electrode modified with gold nanoparticles

This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg^.L^?1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg^.L^?1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy.

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Graphical abstract Hg(II) ions were extracted from a donor phase into an acidic acceptor phase (15 μL) placed in the lumen of a hollow fiber using electromembrane extraction. The acceptor phase was then analyzed using anodic stripping voltammetry.

     

Effect of surface-active compounds on voltammetric stripping analysis at the mercury film electrode

The effects of various organic compounds on the differential-pulse anodic-stripping voltammetric response at the in-situ plated mercury film electrode are explored. These effects vary from metal to metal and from one organic compound to another. The most pronounced effects are observed in measurements of copper. The main effect of the organic compound is to depress the peak current rather than change the peak shape or potential. The differences between the organic interferences observed at the mercury film electrode and those reported at the hanging mercury drop electrode are explained by the different morphology and geometry of the two electrodes. The implications of these interferences for the reliability and feasibility of stripping measurements in natural waters are discussed. Gelatin, camphor, humic acid, starch, agar, sodium dodecyl sulphate and albumin were used as representative organic compounds, and cadmium, lead, and copper as test metal ions.     

Square-wave anodic stripping voltammetric determination of thallium(I) at a Nafion/mercury film modified electrode

A Nafion/mercury film electrode (NMFE) was used for the determination of trace thallium(I) in aqueous solutions. Thallium(I) was preconcentrated onto the NMFE from the sample solution containing 0.01 M ethylenediaminetetraacetate (EDTA), and determined by square-wave anodic stripping voltammetry (SWASV). Various factors influencing the determination of thallium(I) were thoroughly investigated. This modified electrode exhibits good resistance to interferences from surface-active compounds. The presence of EDTA effectively eliminated the interferences from metal ions, such as lead(II) and cadmium(II), which are generally considered as the major interferents in the determination of thallium at a mercury electrode. With 2-min preconcentration, linear calibration graphs were obtained over the range 0.05-100 ppb of thallium(I). An even lower detection limit, 0.01 ppb, were achieved with 5-min accumulation. The electrode is easy to prepare and can be readily renewed after each stripping experiment. Applicability of this procedure to various water samples is illustrated.     

Anodic stripping voltammetric determination of mercury by use of a sodium montmorillonite-modified carbon-paste electrode

A sodium montmorillonite (SWy-2)-modified carbon-paste electrode has been examined for determination of trace levels of mercury. Because of its strong cation-exchange and adsorptive characteristics, SWy-2 greatly improves the sensitivity of determination of Hg(2+). Hg(2+) is preconcentrated and reduced on the modified electrode surface at -0.40 V and then stripped from the electrode surface during the positive potential sweep. The conditions used for determination, e.g. supporting electrolyte, pH, amount of SWy-2, accumulation potential, and accumulation time, were optimized. The peak current was linearly dependent on the concentration of mercury from 1 x 10(-9) to 5 x 10(-7) mol L(-1). The detection limit (signal-to-noise ratio=3) was 1 x 10(-10) mol L(-1) after accumulation for 6 min. When the SWy-2-modified carbon-paste electrode was used to detect mercury in water samples the average recovery was 101.11%.     

Centrifugation: an efficient technique for preconcentration in anodic stripping voltammetric analysis of mercury using a gold film electrode

The effect of centrifugation on the voltammetric behavior of mercury on a gold film electrode was investigated. Mercuric ion was reduced with borohydride to form metallic mercury droplets which were collected on a gold film electrode with the aid of centrifugal force without a carrier material. A special cell was constructed for this purpose. The effect of the amounts of reducing agent, stripping solution, time and speed of centrifugation on the anodic stripping peaks resulting from the re-oxidation of mercury were investigated. The calibration graph for mercury(II) has a regression coefficient of 0.9941; its linear range is from 3.0 pM to 10.0 nM. Due to the effect of accumulation, the detection limit of mercury(II) is as low as 3 pM.     

Stripping voltammetric determination of lead using a glassy-carbon electrode system

The effect of the electrochemical pretreatment of the surface of a glassy-carbon indicator electrode on the electrode response and the repeatability of measurements in the stripping voltammetric determination of lead was studied. It was shown that the analytical signal depends on the nature of an electrolyte used for the pretreatment. The electrolytes that gave the most satisfactory results in the pretreatment were proposed     

Sensitive voltammetric determination of gallium in aluminium materials using renewable mercury film silver based electrode

Simple cyclic renewable silver amalgam film electrode (Hg(Ag)FE), applied for the determination of gallium(III) using differential pulse anodic stripping voltammetry (DP ASV), is presented. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimised. The calibration graph is linear from 5?nM (0.35?µg?L^?1) to 80?nM (5.6?µg?L^?1) for a preconcentration time of 60?s, with correlation coefficient of 0.995. For a Hg(Ag)FE with a surface area of 9.9?mm² the detection limit for a preconcentration time of 120?s is as low as 0.1?µg?L^?1. The repeatability of the method at a concentration level of the analyte as low as 3.5?µg?L^?1, expressed as RSD is 3.2% (n?=?5). The proposed method was successfully applied by studying the synthetic samples and simultaneously recovery of Ga(III) from spiked aluminium samples.     

氨苄青霉素降解产物在汞膜电极上的伏安法研究

考察了氨苄青霉素在酸、碱条件下的降解产物于玻碳汞膜电极上的伏安行为 ,降解产物在醋酸缓冲溶液 ( p H5.5)的底液中均产生了灵敏的阴极还原峰 ,以碱降解条件为好。已将方法应用于模拟样品的分析。     

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.     

Determination of dinoseb by adsorptive stripping voltammetry using a mercury film electrode

An adsorptive stripping voltammetric method for the determination of the pesticide dinoseb (2-sec.-butyl-4,6-dinitrophenol) at the mercury film electrode is described. The deposition of the mercury film on a glassy carbon disk electrode was optimized. The temperature, at which the mercury film was deposited, was demonstrated to have a strong influence on the stripping peaks, the first one being much more intense than the second. A systematic study of the variables affecting the stripping response was carried out by differential pulse voltammetry. The results obtained have been compared with those at the HMDE; a significant improvement in the sensitivity of the method developed with the MFE was observed. Using a 300 s accumulation time, the limits of determination and detection were 3.6 × 10^–10 and 1.1 × 10^–10 mol L^–1, respectively. The effect of the presence of several herbicides on the dinoseb response was also tested. The method has been applied to the determination of the pesticide in spiked apple juice at two concentration levels: 12.0 and 1.2 g L^–1 of juice.     

Adsorptive stripping voltammetric determination of 4-aminophenol at a single-wall carbon nanotubes film coated electrode

A single-wall carbon nanotubes (SWNT)-Nafion film coated glassy carbon electrode (GCE) was described for the determination of 4-aminophenol. In pH 3.0 sodium citrate-HCl buffer, the oxidation peak current of 4-aminophenol increases greatly at the SWNT-Nafion film coated GCE in contrast to that at both bare GCE and Nafion-film coated GCE. Moreover, the oxidation peak potential shifts to more negative potential. All the experimental parameters were optimized for the determination of 4-aminophenol. The oxidation peak current is proportional to the concentration of 4-aminophenol over the range from 5×10⁻⁹ to 2×10⁻⁶ mol l⁻¹. The detection limit is 8×10⁻¹⁰ mol l⁻¹ at 4 min of accumulation. Using the proposed method, 4-aminophenol in water samples was determined.     

The electrochemical stripping determination of tin in aqueous and nonaqueous media after its extraction

The anodic stripping voltammetric and chronopotentiometric determination of tin(IV) in aqueous and nonaqueous medium after its extraction using the rotating disc electrode made of glassy carbon with the mercury film was studied. The optimum composition of nonaqueous medium for the determination of tin is 0.2 M NaBr+5×10^?5M Hg²⁺ in 20 ml of the extract +30 ml of methanol. Tin(IV) was determined by anodic stripping voltammetry or chronopotentiometry down to the concentration 10^?7M. The selective determination of tin was studied. 10^?6M of tin(IV) was determined with an error ±4–5% even in the presence of metals: Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺ (5×10^?3M), Ag⁺ and Pb²⁺ (5×10^?4M), Cu²⁺ (1.5×10^?4M), Sb³⁺ and Bi³⁺ (5×10^?5M).