Determination of total antimony(III,V) by square-wave anodic stripping voltammetry with in situ plated bismuth-film electrode

A sensitive and reliable method is described for the determination of total Sb(III,?V) at traces levels by Osteryoung square-wave anodic stripping voltammery (OSWASV). This method is based on the co-deposition of Sb(III,?V) with Bi(III) onto an edge-plane pyrolytic graphite substrate at an accumulation step. OSWASV studies indicated that the co-deposited antimony was oxidised with anodic scans to give an enhanced anodic peak at about 450?mV vs. Ag/AgCl (sat. KCl). The anodic stripping peak current was directly proportional to the total concentration of antimony in the ranges of 0.01–0.10?µg?L^?1, 0.10–1.0?µg?L^?1 and 1.0–18.0?µg?L^?1 with correlation coefficient higher than 0.995 when 2.0?mol?L^?1 hydrochloric acid was used. The detection limits calculated as S/N?=?3 was 5.0?ng?L^?1 in 2.0?mol?L^?1 hydrochloric acid at 180?s deposition time. The relative standard deviation was 5% (n?=?6) at 0.10?µg?L^?1 level of antimony. The analytical results demonstrate that the proposed method is applicable to analyses of real water samples.     

Determination of trace amount of bismuth(III) by adsorptive anodic stripping voltammetry at carbon paste electrode

A sensitive method is described for the determination of trace bismuth based on the bismuth-bromopyrogallol red (BPR) adsorption at a carbon paste electrode (CPE). The overall analysis involved a three-step procedure: accumulation, reduction, and anodic stripping. Optimal conditions were found to be an electrode containing 25% paraffin oil and 75% high purity graphite powder, a 0.30 mol l⁻¹ HCl solution containing 2.0×10⁻⁵ mol l⁻¹ BPR as supporting medium; accumulation potential and time, −0.10 V, 3 min; reduction potential and time, −0.35 V, 60 s; scan rate 100 mV s⁻¹; scan range from −0.35 to 0.15 V. It was found that the Bi(III)-BPR complex could be accumulated on the electrode surface during the accumulation period. Then the Bi(III) in the Bi(III)-BPR complex on the CPE surface was reduced to Bi(0) during reduction interval and finally reoxidized during the anodic stripping step for voltammetric quantification. Factors affecting the accumulation, reduction, and stripping steps were investigated. Interferences by other ions were studied as well. The detection limit was found to be 5×10⁻¹⁰ mol l⁻¹ with a 3 min accumulation time. The linear range was from 1.0×10⁻⁹ to 5.0×10⁻⁷ mol l⁻¹. Application of the procedure to the determination of bismuth in water and human hair samples gave good results.     

Determination of selenium(IV) by catalytic stripping voltammetry with an in situ plated bismuth-film electrode.

A very sensitive and simple method is presented for the determination of Se(IV) by Osteryang square-wave cathodic stripping voltammery (OSWCSV). The method is based on the reduction of Se(IV) with Bi(III) onto an edge-plane type of pyrolytic graphite substrate, followed by a cathodic potential scan. OSWCSV studies indicate that the reduced selenium produced a distinct catalytic hydrogen wave at -1150 mV vs. Ag/AgCl. The peak height of the catalytic hydrogen wave was directly proportional to the initial Se(IV) concentration in the ranges of 0.1 - 1.0 and 1.0 - 20.0 microg L(-1) (correlation coefficients 0.9800 and 0.9901, respectively) when the optimized parameters were used. A 3sigma detection limit of 0.025 microg L(-1)0 Se(IV) was obtained at 30 s deposition time. The relative standard deviation was 4.0% on replicate runs (n = 12) for the determinations of 0.10 microg L(-1) Se(IV). Analytical results of natural water samples demonstrate that the proposed method is applicable to speciation analysis of Se(IV) and Se(VI).     

Simultaneous determination of mercury and arsenic by anodic stripping voltammetry

An electrochemical method for the simultaneous determinations of Hg^II concentration and total As^III and As^V concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of As^V to As^III, or oxidation of As^III to As^V before stripping analysis takes place. Also, the method for the simultaneous determination of Hg^II concentration and As^III concentration is described. Measurements were performed in 0.1 M HCl using a gold-plated graphite electrode as sensor. Detection limits for both methods are below 0.4 ppb. Relative standard deviation did not exceed 15%. The possible interference by other trace metals was investigated. Analyses of natural water and industrial solutions were made using proposed methods and AAS. The t-test demonstrates that there was no significant difference between the results obtained with these methods. Proposed methods decrease the time of analysis because concentrations of the Hg^II and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of As^V to As^III or oxidation of As^III to As^V decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents.     

Determination of antimony(III) and (V) in natural water by cathodic stripping voltammetry with in-situ plated bismuth film electrode

A method is described for the sequential determination of Sb(III) and Sb(V) using Osteryoung square wave cathodic stripping voltammetry. It employs an in-situ plated bismuth-film on an edge-plane graphite substrate as the working electrode. Selective electro-deposition of Sb(III)/Sb(V) is accomplished by applying a potential of ?500 mV vs. Ag/AgCl, followed by reduction to stibine at a more negative potential in the stripping step. Stripping was carried out by applying a square wave waveform between ?500 and ?1400 mV to the antimony deposited. The stripping peak current at ?1150 mV is directly proportional to the concentration of Sb( III)/Sb(V). The calibration plots for Sb (III) were linear up to 12.0?µg L^?1 depending on the time of deposition. The calibration plots for Sb (V) were linear up to 7.0?µg L^?1, also depending on the time of deposition. The relative standard deviation in the determination of 0.1?µg L^?1 of Sb(III) is 4.0% (n?=?5), and the limit of detection is as low as 2 ng L^?1. In case of 0.1?µg L^?1 Sb(V), the relative standard deviation is 3.0% (n?=?5) and the detection limit also is 2 ng L^?1. The method was applied to the analysis of river and sea water samples.     

Determination of total copper in haemodialysis water by differential-pulse anodic stripping voltammetry

An anodic stripping voltammetric method was developed in order to determine copper in the water used to prepare haemodialysis solutions. The interference from organic matter was overcome by high-pressure bomb mineralization. The electrochemical results were compared with those obtained by using graphite furnace atomic absorption spectrometry and the correlation was excellent (r = 0.983, p < 0.001). The detection limit was 0.2 μg l^?1 copper.     

Speciation of arsenic(III) and arsenic(V) by inductively coupled plasma-atomic emission spectrometry coupled with preconcentration system

A novel and simple flow-based method was developed for the simultaneous determination of As(III) and As(V) in freshwater samples. Two miniature columns with a solid phase anion exchange resin, placed on two 6-way valves were utilized for the solid-phase collection/concentration of arsenic(III) and arsenic(V), respectively. As(III) could be retained on the column after its oxidation to As(V) species with an oxidizing agent. The collected analytes were then sequentially eluted by 2 M nitric acid and introduced into ICP-AES. Potassium permanganate was examined as potential oxidizing agent for conversion of As(III) to As(V). The standard deviation of the analytical signals (peak height) for the replicate analysis (n = 5) of 0.5 μg l⁻¹ solution were 3 and 5% for As(III) and As(V), respectively. The limit of detection (3σ) for both As(III) and As(V) were 0.1 μg l⁻¹. The proposed system produced satisfactory results on the application to the direct analysis of inorganic arsenic species in freshwater samples.     

Determination of trace metoclopramide by anodic stripping voltammetry with nafion modified glassy carbon electrode

A novel method is described for determination of metoclopramide (MCP) by second-derivative adsorptive anodic stripping voltammetry with a nafion-modified electrode. The stripping peak current is proportional to the concentration of MCP over the range 1.2×10⁻⁹–4.6×10⁻⁷ M. The detection limit is 8.0×10⁻¹¹ M with 4-min accumulation. The method has been successfully applied to the determination of MCP in human serum.     

Simultaneous determination of chromium(III) and cadmium(II) by differential pulse anodic stripping voltammetry on a stannum film electrode

A stannum film electrode has been developed for the simultaneous determination of trace levels of chromium(III) and cadmium(II) by differential pulse anodic stripping voltammetry (DPASV). The stannum film electrode was generated in situ by depositing simultaneously the stannum film and the metals obtained by reduction of Cd(II) and Cr(III) at −1.4 V on a glassy carbon electrode. Then, the reduced products were oxidized by scanning the potential of the electrode from −1.4 to −0.4 V using DPASV. The electrode exhibited well-defined and separated stripping signals for both metals accompanied with a low background contribution. The possible mechanism of this design was proposed. Under the optimized working conditions, the detection limit was 2.0 and 1.1 μg l⁻¹ for Cr(III) and Cd(II) at a deposition time of 3 min. Finally, the stannum film electrode was successfully applied to the determination of Cd(II) in tap water with satisfactory results.     

Antimony-film electrode for the determination of trace metals by sequential-injection analysis/anodic stripping voltammetry

The possibility of applying antimony-film modified glassy carbon electrode in sequential-injection analysis (SIA) was investigated with the objective of determining Pb(II) and Cd(II) by anodic stripping voltammetry (ASV). The conditions of antimony-film deposition concerning composition of the plating/carrier solutions, concentrations of Sb(III) and hydrochloric acid, effects of different supporting electrolyte salts, and plating potential were optimized. It was found that the antimony-film deposition on glassy carbon substrate in a sample solution consisting of 750 μg L⁻¹ Sb(III), 0.5 mol L⁻¹ HCl at −1.5 V (vs. Ag/AgCl/3 mol L⁻¹ KCl) yielded a modified electrode suitable for the determination of Pb(II) and Cd(II) at the μg L⁻¹ level. The reproducibility of the analytical signals was characterized by a relative standard deviation lower than 2.8%, and the calculated values of detection limits were 1.2 μg L⁻¹ for Pb(II) and 1.4 μg L⁻¹ for Cd(II). The presence of KSCN in the sample solution offers the possibility of detecting ions with more negative oxidation potentials like Zn(II), Mn(II) or Cr(III). The developed SIA-ASV procedure was compared with the commonly used batch method, and its applicability was tested on a spiked tap water sample.     

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.     

TZAAP-Nafion修饰电极溶出伏安法测定痕量铜

近年来,化学修饰电极以其独特的优越性,在分析测试中具有广阔的应用前景[1-6],因此对于新的修饰剂的研究,以及用修饰电极探讨灵敏度高,选择性好的测定方法具有重要的意义。2[2,3,5-三氮唑偶氮]-5-乙酰基氨基苯酚(2-(2,3,5-triazolylazo)-5-acetam idophenol,简称TZAAP)是一种新合成的有机化合物,其结构式为:由于TZAAP可以和金属离子形成稳定的配合物,在光谱法中可以作为显色剂用于环境及生物样品中微量元素的测定[7,8]。Nafion是一种优良的阳离子交换剂,用作电极修饰材料具有良好的离子交换特性[9]。本文作者制备了TZAAP-Nafion修饰…     

Determination of trace aluminium by adsorptive stripping voltammetry on a preplated bismuth-film electrode in the presence of cupferron

This work reports the use of adsorptive stripping voltammetry (AdSV) for the determination of aluminium on a rotating-disc bismuth-film electrode (BiFE). Al(III) ions in the non-deoxygenated sample were complexed with cupferron and the complex was accumulated by adsorption on the surface of the preplated BiFE. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric excitation signal. 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 aluminium was 0.5 μg l⁻¹ at a preconcentration time of 240 s and the relative standard deviation was 4.2% at the 5 μg 1⁻¹ level for a preconcentration time of 120 s (n = 8). The accuracy of the method was established by analysing water and metallurgical samples.     

Determination of cadmium with a sequential injection lab-on-valve by anodic stripping voltammetry using a nafion coated bismuth film electrode

This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface in bismuth solution, and measured with the subsequential stripping scan. Under optimal conditions, the proposed system responded linearly to cadmium concentrations in a range 2.0-100.0 μg L⁻¹. The detection limit of this method was found to be 0.88 μg L⁻¹. By loading a sample volume of 800 μL, a sampling frequency of 22 determinations h⁻¹ was achieved. The repeatability expressed as relative standard derivation (R.S.D.) was 3.65% for 20 μg L⁻¹ cadmium (n = 11). The established method was applied to analysis of trace cadmium in environmental water samples and the spiked recoveries were satisfactory.     

掺杂硒碳糊电极阳极溶出法测定铋

建立了一种测定痕量铋的新方法,即利用掺杂硒碳糊电极作为工作电极的阳极溶出法.在0.1 mol/L的HCl底液中,Bi3+于+0.05V(vs.Ag/AgCl)出现灵敏的氧化溶出峰,铋离子的浓度在1.0×10-5～1.0×10-9 mol/L范围内其对数值lgc与铋的氧化峰电流值呈线性关系,检出限达1.0×10 -10 ...     

Improved Protocol for Mononitration of Phenols with Bismuth(III) and Iron(III) Nitrates

A simple and efficient multigram procedure was developed for the selective mononitration of various activated phenols. The reaction proceeded smoothly with 0.5 equivalents of Bi(NO₃)₃ · 5H₂O or Fe(NO₃)₃ · 9H₂O in acetone at ambient temperature or at reflux. The desired products were isolated in 62–93% total yield and essentially no overnitrated compounds were detected.     

Determination of antimony (III) and (V) by differential pulse anodic stripping voltammetry

Re-evaluation of DPASV procedures for determining low levels of Sb (III) and Sb (V) in solution identified several problem areas, e.g. anomalous ASV behaviour, possible formation of an intermediate valency state during the analytical cycle, and chemical interactions in acidified test solutions containing both valency states. Specific determination of Sb (III) can be achieved using base solutions composed of 0.2M HCl (detection limit 10 nM) or acetic acid/acetate buffer (detection limit 600 nM). For the determination of Sb (V), analysis in 2M HCl is recommended [with response in 0.2M HCl being used to correct for any Sb (III) present].     

Determination of Cr(VI) in the presence of Cr(III) and humic acid by cathodic stripping voltammetry

A voltammetric procedure in the flow system for determination of traces of Cr(VI) in the presence of Cr(III) and humic acid is presented. The calibration graph is linear from 5×10⁻¹⁰ to 1×10⁻⁷ mol l⁻¹ for an accumulation time of 120 s. The R.S.D. for 1×10⁻⁸ mol l⁻¹ Cr(VI) is 5.3% (n=5). The detection limit estimated from 3σ for a low concentration of Cr(VI) and accumulation time of 120 s is 2×10⁻¹⁰ mol l⁻¹. The method can be used for Cr(VI) determination in the presence of up to 50 mg l⁻¹ of humic acid. The validation of the method was carried out by studying the recovery of Cr(VI) from spiked river water and by the comparison of the results of determination of Cr(VI) in a soil sample. The method cannot be used for analysis of samples containing high concentrations of chloride ions such as seawater and estuarine water.     

Determination of arsenic and antimony in electrolytic copper by anodic stripping voltammetry at a gold film electrode

A simple procedure is described for the determination of arsenic and antimony in electrolytic copper. The copper is digested with nitric acid and copper is separated from arsenic and antimony by passing an ammoniacal solution of the sample through a column of Chelex-100 resin. After digestion with sulphuric acid and reduction to arsenic(III) and antimony(III) with sodium sulphite in 7 M sulphuric acid at 80°C, both arsenic and antimony are deposited at-0.30V and their total is determined by anodic stripping; antimony is then selectively deposited at -0.05 V for anodic stripping. The lower limits of determination are 56 ng As and 28 ng Sb per gram of copper; relative standard deviations (n = 5) are in the ranges 6.1–15.0% for 5.5—0.5 ppm arsenic in copper and 4.1–6.8% for 2.6—0.6 ppm antimony.     

Coulometric stripping potentiometry for arsenic(III)

Calibration-free determination of As^III in the presence of As^V using coulometric stripping potentiometry is described. As^III, in the concentration range 0.01-2 mg/L, is quantitatively reduced to elemental arsenic and simultaneously dissolved in gold codeposited onto a glassy carbon substrate by electrolysis for 4 minutes at −0.50 V (vs. Ag/AgCl (0.01 MCl⁻)) in 12 μL samples containing 3 M hydrochloric acid and 10 mg/L gold(III). Selectivity between arsenic(III) and (V) is achieved by proper control of the deposition potential and by minimizing the gold(III) concentration and the time between addition of gold(III) and commencement of analysis.