玻璃石墨金膜电极电位溶出法测定锡

目前电位溶出法常用的工作电极为汞膜电极,常用的氧化剂为溶解氧或汞(Ⅱ)和铬(Ⅵ)。在伏安溶出法中,采用金膜电极仅用于碲、砷、汞、锗等离子的测定,在电位溶出法中也有报导,但就地镀金膜电极电位溶出法尚未见记载。我们经过研究,成功地采用就地镀金的金膜电极对铜、铋、锑、铅进行了测定,蓝对该方法的机理进行了定量推导和探讨。本文进一步用就地镀金膜电极对锡进行了测定,溶液中的Sn(Ⅳ)和Sn(Ⅱ)首先被还原富集于金膜     

铕离子掺杂类普鲁士蓝复合汞膜电极的制备及溶出分析特性

在铕离子掺杂类普鲁士蓝(Eu-PB)修饰的玻碳电极表面电沉积汞膜,制备了一种新型化学修饰复合汞膜电极GC/Eu-PB/MFE.研究了修饰层厚度、镀汞方式和汞膜成长过程对复合汞膜形成的影响.以Pb2+和Zn2+为探针离子,对复合汞膜电极和常规玻碳汞膜电极的氢过电位值、表面活性物质的影响、汞膜稳定性和金属离子的溶出伏安行为等进行了对比研究.同时,应用该电极结合示差脉冲阳极溶出伏安法对环境水样中的痕量Pb2+进行了测定.结果表明,Pb2+在该复合汞膜电极上的阳极溶出峰电流与其质量浓度在0.8 ～250 μg/L范围有良好的线性关系(r=0.999 5,n=12),检出限为0.2 μg/L,加标回收率为98% ～102%.用该法对国家铅标准物质溶液对比测定,数据的重复性和准确性均令人满意.     

一种扩大汞膜电极可用电位范围的新方法及应用

研究了玻碳汞膜电极在次黄嘌呤溶液中的电化学行为及在此溶液中对抗坏血酸的电催化性能.结果表明:底液中加入一定量的次黄嘌呤能很好地抑制汞在较高的电位下溶出,并且汞膜电极在此溶液中有较好的稳定性,从而扩大了汞膜电极可用电位范围,为在较高电位下应用汞膜电极测定抗坏血酸提供了条件.在pH 1.81缓冲溶液中,抗坏血酸在汞膜电极上于0.25 V处出现灵敏的不可逆氧化峰(以银-氯化银电极作参比电极),峰电流在5×10-5～2.4×10-3mol·L-1范围内与浓度呈线性关系;检出限分别为8×10-6mol·L-1.该方法用于维生素C片剂中抗坏血酸含量的测定,分析结果的相对标准偏差(n=7)为1.3%,回收率在101.2%～104.5%之间.     

微电极研究Ⅵ.碳纤维微电极阳极溶出伏安研究

用电化学方法和扫描电镜对沉积晶体图象的观察,剖析了碳纤维微电极上汞膜的形成过程,提出了优化汞膜的实验条件;导出了碳纤维微汞膜电极上单扫描溶出电流方程式。通过搅拌和支持电解质对溶出峰电流影响的研究,提出了一个简化的分析手续,开发了CFME在ASV中的应用,Cu~(2+),Pb~(2+),In~(3+)和Cd~(2+)同时测定的检测限达3.0,0.6,1.2和0.5ppb,Zn~(2+)的检出限为1.3ppb。     

碳纤维微电极恒电位活化及测定金属离子的研究

碳纤维微电极已被广泛应用于电化学研究和分析测定,该电极尺寸极小,在分析性能上与常规电极有显著不同,在不镀汞的情况下,用碳纤维电极直接测定金属离子几乎没有明显的伏安响应,本文提出用+2.5 V恒电位预先活化碳纤维电极,使测定灵敏度大为提高,在双电极体系和静止溶液中,采用溶出伏安法可测定10~(-9)级金属离子,以同样的方法清洗电极,测定结果重现性良好,由于分析过程中不使用汞,该电极的测定范围大大增加,特别是用于氧化还原电位较正的金属离子测试,根据循环伏安法、扫描电镜和电子能谱的研究,发现碳纤维表面状况在处理前后有很大变化,并与测定灵敏度密切相关。     

以亮绿-Hgl_3~-离子缔合物为电活性物质的汞(Ⅱ)电极

目前,人们已经研制成功许多离子的选择性电极,并获得广泛应用。但有关二价汞选择电极的研究却较少,更未见到应用的实例。较早报导的对二价汞产生响应的电极有:以打萨宗与二价汞螯合物Hg(HD_2)_2的四氯化碳溶液制成的液态电极;Ag_2S和混合硫化物固态膜电极;AgI、AgHgI_4或AgI-Ag_2S固态膜电     

主成分回归-络合滴定法测定混合金属离子

提出了用络合滴定法测定混合金属离子.以汞膜电极为指示电极,银-氯化银电极为参比电极,以标准EDTA溶液滴定混合金属离子溶液.采集-系列指定电位点处滴定剂的体积,并以主成分回归法处理滴定数据.利用本文方法对铜、锌、铅、钻混合溶液进行了测定,结果满意.     

银膜玻碳电极阳极溶出法测定氯化稀土中微量铅

用玻碳电极作工作电极的阳极溶出伏安法,通常需加入10~(-5)M的Hg~(2+)。由于工作溶液都含汞,汞(自溶液中)的挥发以及溶液与人体的接触,仍对操作人员的健康带来危害。试液在测完后倒入下水道,对环境也造成污染。用银膜代替汞膜的研究尚未见文献报导。本文提出在用玻碳电极阳极溶出法测铅时,以银膜代替汞膜,能达到同样的灵敏度与精密度,并且避免了汞的公害。 (一)主要仪器与试荆 1.JPIA型示波极谱仪(成都仪器厂产品)。免去敲击器。     

铋膜电极电位溶出法测定痕量铅、镉、锌

研究了用铋膜电极替代汞膜电极测定痕量重金属元素铅、镉和锌的电位溶出法。实验了同位镀铋膜及测定重金属特别是痕量铅的条件。实验结果表明：铅、镉、锌在铋膜电极上可得到灵敏的电位溶出峰，峰高和溶出电位与汞膜电极法相近，使用铋膜电极可避免使用汞电极带来的环境污染。利用铋膜电极电位溶出法测定了水样及血样中痕量铅的含量。     

电位溶出时间方程式及其实验验证

本文推导了溶出过渡时间与各种实验参数的关系式.在玻碳汞膜电极和玻碳电极上实验了金属离子的价态、氧化剂的种类和浓度、支持电解质浓度、溶液的粘度、明胶、电极面积、汞膜厚度及温度等各种实验参数对溶出过渡时间的影响.对某些二价和三价离子以及还原电位较正的一价离子,实验结果基本与导出的表示式一致,但对一价铊离子实验值与计算值偏差很大,其原因尚待研究.     

Integration of microchip electrophoresis with electrochemical detection using an epoxy-based molding method to embed multiple electrode materials

This paper describes the use of epoxy-encapsulated electrodes to integrate microchip-based electrophoresis with electrochemical detection. Devices with various electrode combinations can easily be developed. This includes a palladium decoupler with a downstream working electrode material of either gold, mercury/gold, platinum, glassy carbon, or a carbon fiber bundle. Additional device components such as the platinum wires for the electrophoresis separation and the counter electrode for detection can also be integrated into the epoxy base. The effect of the decoupler configuration was studied in terms of the separation performance, detector noise, and the ability to analyze samples of a high ionic strength. The ability of both glassy carbon and carbon fiber bundle electrodes to analyze a complex mixture was demonstrated. It was also shown that a PDMS-based valving microchip can be used along with the epoxy-embedded electrodes to integrate microdialysis sampling with microchip electrophoresis and electrochemical detection, with the microdialysis tubing also being embedded in the epoxy substrate. This approach enables one to vary the detection electrode material as desired in a manner where the electrodes can be polished and modified as is done with electrochemical flow cells used in liquid chromatography.     

Effect of the modification of mercuric oxide on the properties of mercury films at HgO-modified carbon paste electrodes

The influence of modifications of the mercuric oxide on the voltammetric properties of mercury film carbon paste electrodes was studied. The mercury film was formed electrochemically from the bulk red or yellow mercuric oxide-modified carbon paste electrodes. Differential pulse anodic stripping voltammetry and optical microscopy in polarised light were used to characterise the properties of the mercury films. The results were compared with those obtained using the conventional preparation of mercury-plated carbon paste electrodes when the mercury film is deposited on the surface of the electrode by reduction of Hg(II) ions in solution utilising a sufficient negative potential. It was shown that the mercury film formed from the yellow modification of the mercuric oxide provides better voltammetric characteristics than the red one owing to the high distribution of its small particles, i.e. the mercury droplets after electrochemical treatment. Such a mercury film has similar properties to those of a mercury film generated from solution. Received: 06 December 1999 / Accepted: 16 March 2000     

Differential-pulse anodic stripping voltammetry of mercury with gold-film micro-electrodes

Cylindrical gold film micro-electrodes are easily produced by plasma-sputtering of gold onto carbon fiber electrodes. The micro-electrodes produced were found to maintain their cylindrical geometry indefinitely, unlike gold wire electrodes of similar dimensions. Application of these electrodes in differential-pulse anodic stripping voltammetry provides a method for quantifying trace levels of mercury(II). Up to 100 μg l^?1 Hg(II) the area of the mercury stripping peak varied linearly with mercury concentration; the detection limit was 3.7 μg l^?1. With more than 100 μg l^?1 Hg(II) a new mercury stripping peak grows in at less positive potentials; its peak height is linear with Hg(II) concentration.     

Determination of Pb and Cu by Anodic Stripping Voltammetry Using Glassy Carbon Electrodes Modified with Mercury or Mercury-Nafion Films

 Two different approaches for the modification of glassy carbon electrodes using a mercury film and mercury-nafion are compared. The mixture of mercury(II) chloride solution with a nafion solution diluted in ethanol is used to coat the polished glassy carbon surface. The modified working electrodes are compared when measuring Pb and Cu in real seawater samples. An optimisation of the parameters during the formation of the films was done to obtain well-defined stripping peaks. The type of inert supporting electrolyte and the pH play an important role on the sensitivity of the measurement. Results for Pb and Cu determinations show the advantages of Hg-nafion modification as an alternative method. These advantages include a shorter modification time, the avoidance of Hg solutions during the formation of the Hg film and an improved sensitivity for Pb determination. Received March 16, 1999. Revision April 24, 2000.     

Stripping Chronopotentiometry with Dry‐Preservable Supporting Electrolyte

The determination of some toxic metals by stripping chronopotentiometry with a supporting solution having an unconventional composition has been investigated with the aim of using such components in disposable measuring cells preservable in dry state and quite ready for use, only needing addition of a small volume of sample. The new supporting solution is prepared with a solid strong acid, p‐toluenesulfonic acid, in the place of the inorganic acids commonly used to improve the cation availability. The other components are, as usual, sodium chloride, which fixes the potential of the screen‐printed silver – silver chloride reference electrode, and mercury(II) chloride as the plating agent. This supporting solution has been tested in batch measurements with the mercury film glassy carbon electrode as well as with screen‐printed carbon‐ink electrodes, either with mercury film or bare. The physical shape of the mercury layer electrolytically deposited on screen‐printed carbon‐ink electrodes from a supporting solution containing 0.1 M p‐toluenesulfonic acid and 0.1 M sodium chloride has been investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) microanalysis. In chronopotentiometric stripping p‐toluenesulfonic acid performs as well as the usual inorganic strong acids, particularly in terms of sensitivity. At 0.1 mol dm^?3 it proved very suitable for the determination of toxic metals, in particular lead(II), at levels down to a few μg dm^?3. The overall results appear promising and can open new avenues for preparing disposable cells for on‐field stripping chronopotentiometric determination of toxic metals.     

A Microcell for Stripping Analysis with Glassy Carbon and Mercury-Plated Glassy Carbon Electrodes

Abstract

A microcell has been constructed for stripping analysis in solution volumes as low as 5 μl, employing a glassy carbon or mercury-plated glassy carbon working electrodes and a three electrode system. Using normal d.c. stripping techniques, as little as 100 picograms of mercury and 10 picograms of lead can be determined. With the more sensitive second harmonic a.c. voltammetric technique, this limit is lowered to 10 picograms of mercury and 1 picogram of lead.     

Polymer-Mercury Coated Screen-Printed Sensors for Electrochemical Stripping Analysis of Heavy Metals

In the perspective of in-field stripping analysis of heavy metals, the use and disposal of toxic mercury solutions (necessary to plate a mercury film on a carbon electrode surface) presents a problem. The aim of this work was the development of mercury coated screen-printed electrodes previously prepared in the lab and ready to use in-field. Thus some commercially available polymers like Nafion®, Eastman Kodak AQ29®, and Methocel® were investigated as mercury entrapping systems for electrochemical stripping analysis of heavy metals. Screen-printed disposable cells with a silver pseudo-reference electrode, a graphite counter electrode, and a graphite working electrode were used. To modify the sensor, the polymer solution was cast onto the carbon working electrode surface. Detection limits of 0.8 and 1 μg/L were obtained for lead and cadmium respectively. Since Methocel® based electrodes showed the best performance, they were used for the analysis of real samples. The results were compared with those obtained using a classical thin mercury film electrode and ICP spectroscopy.

All the experiments reported here were performed in un-deareated solutions as required for in-field analysis.     

Glucose Monitoring by a Biosensor Based on Mercury Thin Film Electrodes

Abstract

Mercury film electrodes consist of a thin film of mercury deposited on an electrode surface (typically glassy carbon) by reduction of a mercury (II) salt in solution. The surface area/volume ratio is larger for the mercury film electrode, and this electrode is more stable than mercury drop electrode, which allows a faster stirring rate to be used in the deposition step. An enzyme electrode is described, based on glucose oxidase immobilized by gelatin and glutaraldehyde and held over a glassy carbon electrode coated with a thin mercury film. This biosensor responds fast and linearly to glucose in a wide concentration range, which is significant because monitoring of glucose levels is a critical component of diabetes care. Certain optimization and characterization studies were carried out. Average value, standard deviation (SD), and variation coefficient (CV) were calculated with the help of the repeatability studies. Finally, glucose content of human blood samples was monitored with the help of the biosensor presented.     

Photoelectrochemical Behavior of Electrodes Containing One-Walled Carbon Nanotubes

Photoelectrochemistry of electrodes containing single-walled carbon nanotubes is studied for the first time ever. Photoemission of electrons from such electrodes illuminated by UV light is discovered. It is established that the photocurrent amplitude as a function of the imposed potential obeys the 5/2 law and that the work function into solution for nanotubes and a mercury electrode coincide to within 0.08 eV. Similarity of electrochemical behavior of intermediates on the nanocarbon and mercury electrodes is shown with the reduction of radicals CH₂Cl as an example.