微分电位溶出分析法应用于金膜电极的研究

本文介绍将微分电位溶出分析法应用于金膜电极,建立了相应的理论体系和应用条件。可使用的金膜厚度在1.8×10~(-7)～4.3×10~(-7)cm范围。检测限较原法降低近两个数量极。用本法测定花生乳中的铜,回收率在94～102%间。     

Voltammetric Determination of Trace Heavy Metals by Sequential-injection Analysis at Plastic Fluidic Chips with Integrated Carbon Fiber-based Electrodes

This work describes a sequential injection analysis (SIA) method for on-line strippping voltammetric determination of Pb(II), Cd(II) and Zn(II) using an injection-moulded electrochemical fluidic chip consisting of 3 conductive carbon fiber-loaded polymer electrodes embedded in a plastic fluidic holder. The sample containing the target metals and a solution containing Bi(III) were aspirated in the holding coil of the SIA manifold. Then, the flow was reversed and the two solutions were directed to the fluidic cell through a mixing coil which induced mixing of the two zones. Upon reaching the cell, simultaneous reduction of the target metals and Bi(III) occurred resulting in the formation of a metal-Bi alloy on the working electrode. Finally, the accumulated metals were stripped off the bismuth-film electrode via a positive potential scan and the oxidation current was recorded. The experimental variables (concentration of the bismuth plating solution, deposition potential, sample volume, stripping mode) were investigated and the potential interferences were assessed. The limits of quantification were 2.8 μg L⁻¹ for Pb(II), 3.6 μg L⁻¹ for Cd(II) and 4.2 μg L⁻¹ for Zn(II) and the the within-chip and between-chip % relative standard deviations were ≤6.3 % and ≤14 %, respectively. Finally, the sensor was applied to the determination of trace metals in a fish food sample.     

支撑液膜体系渗透系数和反萃液酸度的关系

A new permeability coefficient equation was theoretically derived. It contains both the acid concentration of feed solution and the carrier concentration as well as the acid concentration of stripping solution. The relationship of permeability coefficient and acid concentration of stripping solution was further confirmed by the experimental results of Co2+、Ni2+、 Er3+ ions transporting through the supported liquid membranes.     

槲皮素化学修饰碳糊电极吸附溶出伏安法测定痕量铅

建立了用槲皮素修饰碳糊电极测定痕量铅的新方法 ,在 0 .1 0mol L甲酸盐缓冲液 (pH 4.3 )中 ,于 -0 .1 0V(vs.SCE)搅拌富集 ,再在 -0 .70V静止还原 40s后 ,阳极化扫描 ,于 -0 .42V左右获得一灵敏的铅阳极溶出峰。在最佳条件下 ,富集不同时间 ,其二次导数峰电流与Pb2 + 在 1 .0× 1 0 - 8～ 8.0× 1 0 - 7mol L和 2 .0× 1 0 - 9～ 6.0× 1 0 - 8mol L两个范围内呈线性关系 ,检出限为 8.0× 1 0 - 1 0 mol L(S N =3 )。同时初步探讨了电极反应机理。     

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.     

Determination of Mercury by Chronopotentiometric Stripping Analysis Using Glassy Carbon Vessel as a Working Electrode

In this work chronopotentiometric stripping analysis of mercury was performed using a process vessel of glassy carbon as a working electrode. Experimental parameters for both steady and rotating vessel were investigated and compared. Relative sensitivity as well as the sharpness of the analytical signal was better when the rotation of the process vessel was performed. The new design provided better sensitivity when compared to both stationary and rotating glassy carbon disk electrodes. Detection limit obtained for the electrolysis time of 600 s was 0.1 ng/L of Hg(II). The accuracy of the technique was confirmed by analyzing the standard reference material – tomato leaves.     

阴极溶出伏安法测定异烟肼的研究

报道了吸附阴极溶出伏安法测定异烟肼。探讨了电极反应机理。在０．０１ｍｇｏｌ／Ｌ硼砂底液中，峰电位为－１．４０Ｖ。峰电流与异烟肼浓度在４．０＊１０＾－７－１．５＊１０＾－５ｍｏｌ／Ｌ范围内呈良好的线性关系，相关系为０．９９１３。该方法用于异烟肼片剂的测定，获得满意结果。     

悬汞电极1.5次微分吸附溶出法测定痕量雌激素

雌激素与亚硝酸钠在一定条件下反应,其硝基衍生物具有良好的电活性,能在汞电极上吸附还原.在0.01 mol/L的硼砂介质中,还原电流大小与雌激素的浓度在1×10~(-6)～1×10~(-9)mol/L范围内有较好的线性关系.用1.5次微分溶出法可测定2×10~(-10)mol/L的雌激素.此法已应用于孕妇尿中雌三醇的测定,结果良好.     

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.     

预镀铋膜修饰铂电极差分脉冲溶出伏安法测定痕量铅、镉

采用预镀铋膜法修饰铂电极,用该电极对痕量Pd、Cd同时进行了差分脉冲溶出伏安法测定,Pd、Cd在富集中和铋形成类似于汞齐的合金,溶出峰良好。讨论了在不同沉积液和沉积时间下得到的铋膜电极的性能和富集时间、富集电位及底液pH对金属离子测定的影响。在优化的实验条件下,分别对10~100μg/L、20~200μg/L和50~500μg/L3个不同浓度系列的Pb2 、Cd2 进行了同时测定,Pb、Cd溶出峰电流与Pb2 、Cd2 浓度呈良好的线性关系(r≥0.999),Pb2 、Cd2 浓度的线性范围均为10~500μg/L;富集时间为180 s时,Pb2 、Cd2 的检出限分别为0.38μg/L和0.82μg/L。利用本方法测定了蔬菜中Pb的含量,并与原子荧光分析法做了对比,结果令人满意。     

Catalytic Adsorptive Stripping Voltammetry at a Carbon Paste Electrode for the Determination of Amiodarone

Voltammetry using solid electrodes usually suffers from the contamination due to the deposition of the redox products of analytes on the electrode surface. The contamination has resulted in poor reproducibility and overelaborate operation procedures. The use of the chemical catalysis of oxidant on the reduction product of analyte not only can eliminate the contamination of analyte to solid electrodes but also can improve the faradaic response of analyte. This work introduced both the catalysis of oxidant K2S2O8 and the enhancement of surfactant Triton X-100 on the faraday response of amiodarone into an adsorptive stripping voltammetry at a carbon paste electrode for the determination of amiodarone. The method exhibits high sensitivity, good reproducibility and simple operation procedure. In 0.2 mol·L^-1 HOAc-NaOAc buffer （pH=5.3） containing 2.2×10^-2 mol·L^-1 K2S2O8 and 0.002% Triton X-100, the 2.5th-order derivative stripping peak current of the catalytic wave at 0.3 V （vs. Ag/AgCl） is rectilinear to amiodarone concentration in the range of 2.0×10^-10-2.3×10^-8 mol·L^-1 with a detection limit of 1.5×10^-10 mol·L^-1 after accumulation at 0 V for 30 s.     

Indirect Determination of Trace Copper(II) by Adsorptive Stripping Voltammetry with Zincon at a Carbon Paste Electrode

Traces of copper(II) can be determined by adsorptive stripping voltammetry using 2‐carboxy‐2′‐hydroxy‐5′‐sulfoformazyl benzene (Zincon) as complex forming reagent. First in phosphate buffer pH 6.4, copper(II)‐Zincon complex was adsorbed on carbon paste electrode (CPE) with an accumulation potential of 0.6 V. Following this, adsorbed complex was oxidized and detected by differential pulse voltammetric (DPV) scan from 0.6 to 1.0 V. The effective parameters in sensor response were examined. The detection limit (DL) of copper(II) was 1.1 μg/L and relative standard deviations (RSDs) for 10 and 200 μg/L Cu(II) were 1.81 and 1.03%, respectively. The calibration curve was linear for 2–220 μg/L copper(II). The resulting CPE does not use mercury and therefore, has a positive environmental benefit. The method, which is reasonably sensitive and selective, has been successfully applied to the determination of trace amount of copper in water and human hair samples.     

Adenine Determination in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Highly sensitive, simple and inexpensive techniques of adenine determination are particularly interesting in relation to the present development of ATP and DNA sensors. A nanomolar concentration of adenine can be determined in the presence of copper. For an accumulation time of 30 minutes, the detection limit found was 0.22 ppb (1.63×10^?9 M). The method is based on controlled adsorptive accumulation of adenine‐copper at thin‐film mercury electrode followed by linear scan voltammetric measurement of the surface species. By applying a condition time of 60 s at ?0.9 V, the same thin‐film can be used over several measurements. Optimum experimental conditions were found to be the use of a 5.0×10^?3 M NaOH solution, an accumulation potential over the ?0.20 to ?0.40 V range, and a scan rate of 100 mV s^?1. The response of adenine‐copper is linear over the concentration range 20–100 ppb. The more convenient ways to measuring adenine in the presence of metals and other nitrogenated bases were also investigated. The adenosine triphosphate (ATP) or deoxyribonucleic acid (DNA) are first treated with acid (e.g., 0.1 M perchloric acid), and the acid‐released adenine (without separation from others products of the degradation) is directly determined by adsorptive stripping voltammetry.     

DNA Determination in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

A stripping method for the determination of single‐stranded DNA in presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of adenine (from acid‐treated DNA) at thin‐film mercury electrode followed by linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0×10^?3 M NaOH solution, an accumulation potential of ?0.40 V and a scan rate of 200 mV s^?1. The response of adenine–copper is linear over the concentration range 50–250 ppb. For an accumulation time of 15 minutes, the detection limit was found to be 4 ppb. The more convenient relation to measuring the ssDNA in presence of metals and nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of adenosine‐triphosphate (ATP) and amino acids.     

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.     

High Sensitivity and Reproducibility of a Bismuth/Poly(bromocresol purple) Film Modified Glassy Carbon Electrode for Determination of Trace Amount of Cadmium by Differential Pulse Anodic Stripping Voltammetry

This work described a novel type of bismuth/poly(bromocresol purple) film modified glassy carbon electrode (denoted as Bi/Poly(BCP)/GCE) for anodic stripping analysis of trace Cd²⁺. The Bi/Poly(BCP)/GCE was fabricated in situ by depositing simultaneously bismuth and cadmium by reduction at ?1.20 V on the poly(BCP) film using a differential pulse voltammetry. Under the optimum conditions, the anodic stripping peak current response increased linearly with the Cd²⁺ concentrations in a range of 2.0×10^?8–1.0×10^?7 M and 1.0×10^?7–6.0×10^?6 M in 0.1 M NaAc‐HAc buffer solution (pH 5.0) with the detection limit of 6.5×10^?9 M (S/N=3). The Bi/poly(BCP)/GCE performed good reproducibility and high sensitivity. Finally, this proposed method was successfully applied to determine the concentration of Cd²⁺ in water samples.     

Fast Mapping of Gunshot Residues by Batch Injection Analysis with Anodic Stripping Voltammetry of Lead at the Hanging Mercury Drop Electrode

The forensic analysis of lead in gunshot residues (GSR) sampled on the hands of potential shooters is rendered faster, simpler and less expensive by a new batch injection analysis (BIA) method, based on differential pulse anodic stripping voltammetry (DPASV). A simple “J” shaped adaptor was designed to direct the flux of the analyte injected with a micropipettor onto the hanging mercury drop electrode of any commercial electrode stand. Sampling methods for GSR were compared and lifting with adhesive tape was elected for field use. The tapes are glued on polyethylene screens and stored in capped vials. Sampling with multiple strips provides coarse mapping of the distribution of lead on the shooter's hands. After a dissolution/extraction step with chloroform/aqueous 0.10 mol L^?1 HCl, 100 μL of the aqueous phase are injected during 25 s for accumulation of lead on the HMDE at ?0.60 V (vs. Ag/AgCl). A detection limit of 20 ng/mL of Pb(II), outreaching for GSR analysis, is reached without oxygen removal, at a frequency of 20 injections per hour. Results for sequences of shootings with a revolver and a pistol are presented.     

Determination of Cysteine in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Abstract

A stripping method for the determination of cysteine in the presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of cysteine at mercury film electrode followed by linear cyclic voltammetry scan measurement of the surface species. Optimum experimental conditions were found to be the use of a 1×10^?3 M NaOH solution, an accumulation potential of ?0.50 V and a scan rate of 200 mV. s^?1. The response of cysteine is linear over the concentration range 0.04–0.20 ppm. For an accumulation time of 15 minutes, the detection limit was found to be 0.9 ppb (7.4×10^?9 M). The more convenient relation to measuring the cysteine in presence of metals, and others amino acids were also investigated. The utility of the method is demonstrated by presence of casein and ATP.     

In Vivo Monitoring of the Thiols in Rat Striatum by Liquid Chromatography with Amperometric Detection at a Functionalized Multi‐Wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode (CME) was fabricated, which was based on the immobilization of multi‐wall carbon nanotubes fuctionalized with carboxylic group (MWNT‐COOH). The results indicated that the CME exhibited efficiently electrocatalytic oxidation for L ‐cysteine and glutathione with relatively high sensitivity, stability and long‐life. Coupled with HPLC, the MWNT‐COOH CME was utilized for amperometric detection of the thiols. The peak currents of L ‐cysteine and glutathione were linear to their concentrations ranging from 3.0×10^?7 to 1.0×10^?3 mol/L with the calculated detection limit (S/N=3) of 1.2×10^?7, 2.2×10^?7 mol/L, respectively. The method had been successfully applied to assess the contents of L ‐cysteine and glutathione in rat striatal microdialysates.