Microscopic and electrochemical characterization of lead film electrode applied in adsorptive stripping analysis

Lead film electrodes (PbFEs) deposited in situ on glassy carbon or carbon paste supports have recently found application in adsorptive stripping voltammetric determination of inorganic ions and organic substances. In this work, the PbFE, prepared in ammonia buffer solutions, was investigated using scanning electron microscopy, atomic force microscopy and various voltammetric techniques. The microscopic images of the lead films deposited on the glassy carbon substrate showed a considerable variability in microstructure and compactness of the deposited layer depending on the selected experimental conditions, such as the concentration of Pb(II) species, the nucleation and deposition potential, and the time applied. The catalytic adsorptive systems of cobalt and nickel in a solution containing 0.1 ammonia buffer, 2.5 × 10⁻⁵ M nioxime and 0.25 M NaNO₂ were employed to investigate the electrochemical characteristics and utility of the in situ prepared lead films.The optimal parameters, i.e. the lead concentration in the solution, the procedure of film removal, and the time and potential of lead nucleation and film deposition for the adsorptive determination of metal traces, were selected, resulting in the very good reproducibility (RSD = 4.2% for 35 scans) of recorded signals. The voltammetric utility of the lead film electrode was compared to that of glassy carbon, mercury film and bismuth film electrodes, and was subsequently evaluated as superior.     

Anodic stripping voltammetric measurement of trace heavy metals at antimony film carbon paste electrode

The antimony film carbon paste electrode (SbF-CPE) was prepared in situ on the carbon paste substrate electrode as a “mercury-free” electrochemical sensor. Its aptitude for measuring some selected trace heavy metals has been demonstrated in combination with square-wave anodic stripping voltammetry in non-deaerated model solutions of 0.01 M hydrochloric acid with pH 2. Some important operational parameters, such as deposition potential, deposition time, and concentration of antimony ions were optimized, and the electroanalytical performance of the SbF-CPE was critically compared with both bismuth film carbon paste electrode (BiF-CPE) and mercury film carbon paste electrode (MF-CPE) using Cd(II) and Pb(II) as test metal ions. In comparison with BiF-CPE and MF-CPE, the SbF-CPE exhibited superior electroanalytical performance in more acidic medium (pH 2) associated with favorably low hydrogen evolution, improved stripping response for Cd(II), and moreover, stripping signals corresponding to Cd(II) and Pb(II) at the SbF-CPE were slightly narrower than those observed at bismuth and mercury counterparts. In addition, the comparison with antimony film electrode prepared at the glassy carbon substrate electrode displayed higher stripping current response recorded at the SbF-CPE. The newly developed sensor revealed highly linear behavior in the examined concentration range from 5 to 50 μg L⁻¹, with limits of detection (3σ) of 0.8 μg L⁻¹ for Cd(II), and 0.2 μg L⁻¹ for Pb(II) in connection with 120 s deposition step, offering good reproducibility of ±3.8% for Cd(II), and ±1.2% for Pb(II) (30 μg L⁻¹, n = 10). Preliminary experiments disclosed that SbF-CPE and MF-CPE exhibit comparable performance for measuring trace concentration levels of Zn(II) in acidic medium with pH 2, whereas its detection with BiF-CPE was practically impossible. Finally, the practical applicability of SbF-CPE was demonstrated via measuring Cd(II) and Pb(II) in a real water sample.     

Pb~(2+)在掺硼金刚石膜电极上的电化学行为

为了充分发挥掺硼金刚石膜(BDD)电极在分析检测工业废水中重金属离子的优势,利用BDD电极作为工作电极,采用线性扫描阳极溶出伏安法测定水溶液中的铅离子,考察了硝酸、硫酸、高氯酸、盐酸4种酸体系对铅离子分析测试的影响。结果发现,在实验室条件下检测铅离子最优的支持电解质体系是硫酸,并且与其他3种酸(硝酸、盐酸、高氯酸)相比,硫酸更加稳定,不具挥发性。     

Novel electrode for electrochemical stripping analysis based on carbon paste modified with bismuth powder

Bismuth-powder modified carbon paste electrode (Bi-CPE) is presented as an attractive “mercury-free” sensor applicable in electrochemical striping analysis of selected heavy metals. The electrode paste was prepared as a mixture of finely powdered metallic bismuth together with graphite powder and silicon oil. The Bi-CPE was characterized in nondeaerated solutions containing Cd(II) and Pb(II) at the μg/L level in conjunction with square-wave anodic stripping voltammetry. The electrode exhibited well-defined and separated stripping signals for both metals accompanied with a low background contribution, and a reproducibility of 5.6 and 6.0% (n = 12) for 20 μg/L Cd(II) and Pb(II), respectively. The Bi-CPE exhibited superior performance in comparison to the bare carbon paste electrode (CPE) and the bismuth paste electrode (BiPE) and surprisingly, yielded a higher response than the in situ prepared bismuth-film carbon paste electrode. The electrode displayed excellent linear behavior in the examined concentration range from 10 to 100 μg/L Cd(II) + Pb(II) (R² = 0.998 for both), with limits of detection of 1.2 μg/L for Cd(II) and 0.9 μg/L for Pb(II). The electroanalytical performance of Bi-CPE was successfully tested in a real sample of tap water spiked with Cd(II) and Pb(II).     

铋膜电极阳极溶出伏安法测食盐中锌含量

用铋膜电极代替汞膜电极可避免环境污染。采用玻碳电极同位镀铋在酸性的KSCN介质中测定食盐中锌,结果峰形好、灵敏度高、峰电流值大,检测限为7．8×10^-8mol／L,线性范围为2．0×10^-6mol／L～1．3×10^-5mol／L,加标回收率为92．2％-102．2％。     

Determination of trace selenium by differential pulse adsorptive stripping voltammetry at a bismuth film electrode

The differential pulse adsorptive stripping voltammetric behavior of selenium (IV)-p-aminobenzene sulfonic acid-cetyltrimethylammonium bromide system at a bismuth-coated glassy carbon electrode (BiFE) has been investigated. A well-defined and sensitive stripping peak of the selenium (IV)-p-aminobenzene sulfonic acid complex was observed at −0.76 V (vs. SCE) in a 0.15 mol/L acetate solution (pH 2.9) at a deposition potential of −0.40 V (for 120 s). The linear range was 2-30 μg/L and the detection limit for an accumulation time of 300 s was 0.1 μg/L. This method was applied to determine the trace amount of selenium in the samples.     

Signal splitting in the stripping analysis of heavy metals using bismuth film electrodes: Influence of concentration range and deposition parameters

The stripping signals of Pb(II), Cd(II) and Zn(II) in a bismuth film electrode (BiFE) ex situ plated on glassy carbon support were studied by differential pulse anodic stripping voltammetry and constant-current stripping chronopotentiometry. Regular signals were measured for Pb(II), with a good linearity inside a wide concentration range. In contrast, Cd(II) and Zn(II) produce two overlapping signals, one predominating at low metal concentrations and the other at high metal concentrations. For the detailed study of such peak splitting, multivariate curve resolution by alternating least squares has been used concluding that the total area becomes linear with metal concentration in both situations. The reasons of the peak splitting seem to be related to the accumulation of the reduced metal on BiFE in different ways. Even with that complication, the fact that the linear relationship total area versus concentration is hold reinforces the applicability of BiFE for the determination of total concentrations of metal ions inside a wider concentration range than that initially expected. However, the coexistence of signals at different characteristic potentials anticipates important difficulties in the analysis of potential shifts caused by heavy metal complexation.     

利用超声波阳极溶出伏安法测定痕量汞

以阳极溶出伏安法研究了超声波作用下汞在金电极上的电化学行为,建立了痕量汞的超声波-阳极溶出伏安法。采用超声波增加了汞的溶出峰电流,提高了方法的灵敏度,在优化实验条件下,汞离子浓度在0～25μg/L范围内,线性方程为I=1.08c+0.27,(μg/L,R=0.998),加入标准汞溶液为6μg/L时,测量值的重复性和精确度都在5%以内。常见金属离子一般不干扰,方法简便快速。     

Carbon nanotube-modified glassy carbon electrode for anodic stripping voltammetric detection of Uranyle

A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) is described for the measurement of trace levels of uranium by anodic stripping voltammetry. In a pH 4.4 NaAc-Hac buffer containing 0.010 mol L⁻¹ Mg(NO₃)₂, UO₂ ²⁺ was adsorbed onto the surface of a MWNT film coated glassy carbon electrode and then reduced at −0.40 V vs. Ag/AgCl. During the positive potential sweep the reduced uranium was oxidized and a well-defined stripping peak appeared at +0.20 V vs. Ag/AgCl. Low concentrations of Mg²⁺ significantly enhanced the stripping peak currents since they induced UO₂ ²⁺ to adsorb at the electrode surface. The response was linear up to 1.2 × 10⁻⁷ mol L⁻¹ and the relative standard deviation at 2.0 × 10⁻⁸ mol L⁻¹ uranium was 5.2%. Potential interferences were examined. The attractive behavior of the new “mercury-free” uranium sensor holds promise for on-site environmental and industrial monitoring of uranium.     

Antimony powder-modified carbon paste electrodes for electrochemical stripping determination of trace heavy metals

A new type of the antimony electrode based on a carbon paste bulk-modified with antimony powder (Sb-CPE) is presented for the determination of cadmium(II) and lead(II) ions at the microgram-per-liter concentration level, when using square-wave anodic stripping voltammetric or stripping chronopotentiometric protocol. The Sb-CPE was prepared by mixing fine antimony powder, carbon powder, and silicon oil, thus combining typical features of the carbon paste material with specific electrochemical properties of antimony. Key-operational parameters, including the amount of antimony powder in the carbon paste mixture, effect of the deposition potential and deposition time, were optimized and electroanalytical performance of the Sb-CPE in nondeaerated solution of 0.01 M hydrochloric acid (pH 2) was compared with related bismuth powder-modified carbon paste electrode (Bi-CPE) and with in situ prepared antimony film carbon paste electrode (SbF-CPE). The electrode of interest exhibited well-developed signals and highly linear calibration plots for both metal ions tested. In addition, favorable limits of detection were achieved; namely: 1.4 μg L⁻¹ for Cd(II) and 0.9 μg L⁻¹ for Pb(II). The applicability of the new electrode was demonstrated on the analysis of tap water (spiked sample). Besides voltammetric measurements, the Sb-CPE was preliminary tested also under chronopotentiometric stripping mode in deoxygenated solutions, revealing also an excellent electroanalytical performance.     

Sensitive determination of Cd and Pb by differential pulse stripping voltammetry with in situ bismuth-modified zeolite doped carbon paste electrodes

Here we investigated the analytical performances of the bismuth-modified zeolite doped carbon paste electrode (BiF-ZDCPE) for trace Cd and Pb analysis. The characteristics of bismuth-modified electrodes were improved greatly via addition of synthetic zeolite into carbon paste. To obtain high reproducibility and sensitivity, optimum experimental conditions for bismuth deposition were studied. Voltammetric responses of the BiF-ZDCPEs prepared with different ratios of zeolite, carbon powder, and silicone, were examined under same conditions. The in situ plated (zeolite/graphite powder/silicone, 10/190/80 w/w) BiF-ZDCPEs exhibited the most sensitive response to Cd and Pb in 0.10 M acetate buffer (pH 4.5). The detection limits of the modified electrode were 0.08 μg L⁻¹ for Cd(II) and 0.10 μg L⁻¹ for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120 s under optimal conditions, respectively. The modified electrode showed well linear response to both Cd(II) and Pb(II) over the concentration range from 1.0 to 20.0 μg L⁻¹. The BiF-ZDCPEs were successfully applied to the determination of Cd(II) and Pb(II) in real samples, and the results were in agreement with those of atomic absorption spectroscopy (AAS).     

铋膜玻碳电极阳极溶出伏安法测定异烟肼的研究

研究了异烟肼在铋膜玻碳电极上的电化学行为检测方法。在0.1mol/L pH=4.5的HAc—NaAc缓冲溶液的底液中,通过富集,用铋膜玻碳电极进行阳极溶出伏安法测定异烟肼。异烟肼的阳极峰电位为-1.02V(vs.SCE),峰电流与异烟肼的浓度在1.6×10~(-7)～8.0×10~(-5)mol/L范围内呈良好的线性关系。该方法的检出下限为8.0×10~(-8)mol/L。对异烟肼含量用本法进行了测定,获得了满意的结果。本方法的优点是成本低,操作方便,重现性好以及检测下限低。     

Insights into the simultaneous chronopotentiometric stripping measurement of indium(III), thallium(I) and zinc(II) in acidic medium at the in situ prepared antimony film carbon paste electrode

The simultaneous measurement of microgram per liter concentration levels of indium(III), thallium(I) and zinc(II) at the antimony film carbon paste electrode (SbF-CPE) is demonstrated. The antimony film was deposited in situ on a carbon paste substrate electrode and employed in chronopotentiometric stripping mode in deoxygenated solutions of 0.01 M hydrochloric acid (pH 2). The chronopotentiometric stripping performance of the SbF-CPE was studied and compared with constant current chronopotentiometric stripping and anodic stripping voltammetric operation. In comparison with its bismuth and mercury counterparts, the SbF-CPE exhibited advantageous electroanalytical performance; namely, at the bismuth film electrode, the measurement of zinc(II) was practically impossible due to hydrogen evolution, whereas the mercury film electrode exhibited a poorly developed signal for thallium(I). The SbF-CPE revealed favorable calculated LoDs (3σ) of 1.4 μg L⁻¹ for thallium(I) and 2.4 μg L⁻¹ for indium(III) along with good linear response in the examined concentration range from 10 to 100 μg L⁻¹ with correlations coefficients (R²) of 0.992 for thallium(I) and 0.994 for indium(III) associated with a 120 s deposition time. The chronopotentiometric stripping performance of the SbF-CPE was characterized also by satisfactory reproducibility of 1.62% for indium(III), 3.96% for thallium(I) and 2.11% for zinc(II) (c = 40 μg L⁻¹, n = 11).     

金电极线性扫描溶出伏安法测定菠菜中的重金属Pb

采用金电极线性扫描溶出伏安法对菠菜中的重金属Pb进行测定,结果显示对Pb(Ⅱ)测定具有较高准确度,检出限为1.5×10-6g·L-1,回收率在97.4%~102.6%,RSD为2.36%。该法仪器简单、操作简便,测定Pb的灵敏度可达到原子吸收法水平,通过改善工作电极富集能力,进一步提高灵敏度,即可实现多种元素的连续快速测定。     

Nanomolar detection of rutin based on adsorptive stripping analysis at single-sided heated graphite cylindrical electrodes with direct current heating

A single-sided heated graphite cylindrical electrode (ss-HGCE) was designed. Compared to previous alternative current (AC) heating, much simpler and cheaper direct current (DC) heating supplier was adopted for the first time to perform adsorptive accumulation of rutin at ss-HGCE at elevated electrode temperature. This offers great promise for low cost, miniaturization and high compatibility with portability. The square wave voltammetry (SWV) stripping peak current was enhanced with increasing the electrode temperature only during preconcentration step. This enhancement was contributed to the forced thermal convection induced by heating the electrode rather than the bulk solution, which is able to improve mass transfer and facilitate adsorption hence enhance stripping response. A detection limit of 1.0 × 10⁻⁹ M (S/N = 3) could be obtained at an electrode temperature of 48 °C during 5 min accumulation, one magnitude lower than that at 28 °C (room temperature). This is the lowest value at carbon-based electrodes for rutin determination as we know. Such novel method was also successfully used to determine rutin in pharmaceutical tablets.     

In situ bismuth-film electrode for square-wave anodic stripping voltammetric determination of tin in biodiesel

A bismuth-film electrode (BiFE) was applied in square-wave anodic stripping voltammetry (SWASV) in order to determine Sn (IV) in biodiesel samples. In situ simultaneous deposition of tin and bismuth at −1.2 V for 90 s was carried out in a supporting electrolyte containing 0.1 mol L⁻¹ acetate buffer (pH 4.5) and 1.73 mmol L⁻¹ caffeic acid as the complexing agent. A single well-defined anodic stripping peak was observed at −0.58 V for the oxidation of Sn to Sn (II), which was used as the analytical signal. The calibration curve was obtained in the concentration range of 0.17–7.83 μmol L⁻¹ with the detection limit being 0.14 μmol L⁻¹ (r = 0.9990). Repeatability and reproducibility for the measurement of the current peak were characterized by relative standard deviations of 3.6% and 4.1%, respectively, for a 5.0 μmol L⁻¹ Sn (IV) solution (n = 10). The method was validated by comparing the results obtained with those provided by application of the atomic absorption spectroscopy technique.     

铋膜电极差分脉冲溶出伏安法测定苯甲酸钠中的铅

通过铋膜修饰的玻碳电极,建立了苯甲酸钠中铅的差分脉冲溶出伏安分析法。实验结果表明,在pH 4.0的HAc-NaAc缓冲介质中,-1.1 V富集300 s后,溶出峰电流与Pb2 浓度在5-1 000μg/L范围内呈线性关系,相关系数r=0.995 6,在实际样品测量中,回收率在95.4%-103.5%之间,相对标准偏差为3.44%。     

阳极溶出伏安法测定硫酸锌中的铅和镉

采用玻碳电极为工作电极，以醋酸钠－醋酸－氯化钾溶液为底液，用二次导数阳极溶出伏安法测定了硫酸锌中的微量铅和镉，峰电位分别为－0．43V（Vs,SCF)和－0．62V（Vs,SCE)，线性范围分别为0－2．0μg/925mL)和0－0．8μg/(25mL)，方法准确，快速、简便。     

微分脉冲阳极溶出伏安法测定氢溴酸右美沙芬

应用循环伏安法和微分脉冲阳极溶出伏安法在玻碳电极上对氢溴酸右美沙芬的伏安行为进行了研究。实验结果表明,在pH6.5的B-R(Britton-Robinson)缓冲底液中,氢溴酸右美沙芬在+1.01 V(vs.Ag/AgCl)处有一明显的氧化峰,在4.0×10-6~8.0×10-5mol/L范围内与峰电流呈良好的线性关系(r=0.995 1),检出限为5.6×10-7mol/L。用该方法对氢溴酸右美沙芬片进行了测定,回收率为98.6%~102.9%,结果令人满意,还对其电极反应机理进行了初步探讨。     

阳极溶出伏安法同时测定海水中铜、铅、镉、锌

采用微分脉冲阳极溶出伏安法同时测定了海水中Cu、Pb、Cd、Zn4种痕量元素,在选定最佳实验条件下,通过标准加入法对海水的Cu、Pb、Cd、Zn进行分析,其相对标准偏差分别为5.6%、4.6%、1.80%、1.98%,而回收率分别为98.0%～105.6%、95.3%～106.5%、90.0%～107.4%和90.8%～103.5%,测定结果令人满意。