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Electrochemical Properties of Silver–Copper Alloy Microelectrodes for Use in Voltammetric Field Apparatus Silje M

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Electrochemical Properties of Silver–Copper Alloy Microelectrodes for Use in Voltammetric Field Apparatus Silje M Electrochemical properties of silver–copper alloy microelectrodes for use in voltammetric field apparatus Silje M. Skogvold, Mikkelsen Øyvind, Billon Gabriel, Cédric Garnier, Lesven Ludovic, Jean-Francois Barthe To cite this version: Silje M. Skogvold, Mikkelsen Øyvind, Billon Gabriel, Cédric Garnier, Lesven Ludovic, et al.. Elec- trochemical properties of silver–copper alloy microelectrodes for use in voltammetric field apparatus. Analytical and Bioanalytical Chemistry, Springer Verlag, 2006, 384, pp.1567 - 1577. 10.1007/s00216- 006-0334-4. hal-01096812 HAL Id: hal-01096812 https://hal-univ-tln.archives-ouvertes.fr/hal-01096812 Submitted on 5 Jan 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Anal Bioanal Chem (2006) 384: 1567–1577 DOI 10.1007/s00216-006-0334-4 ORIGINAL PAPER Silje M. Skogvold . Øyvind Mikkelsen . Gabriel Billon . Cedric Garnier . Ludovic Lesven . Jean-Francois Barthe Electrochemical properties of silver–copper alloy microelectrodes for use in voltammetric field apparatus Received: 30 September 2005 / Revised: 25 December 2005 / Accepted: 27 January 2006 / Published online: 21 March 2006 # Springer-Verlag 2006 Abstract Microelectrodes of silver–copper alloys have solution (pH 8.6) only one peak resulting from reduction of been evaluated for use in voltammetric analyses. Increased nitrate was observed. Furthermore, the use of alloy overpotential towards the hydrogen overvoltage reaction electrodes containing 17% Cu was tested in real samples, (HER) was found as a function of increased copper content by installing it in a voltammetric system for monitoring of in the silver. A study of oxidizing products by cyclic zinc and lead in a polluted river, the river Deûle, near the voltammetry (CV) in NaOH solution showed ten anodic town of Douai in northern France. Results were found to be and eight cathodic peaks which are described in the present in agreement with parallel measurements carried out by paper. The behaviour of these alloy electrodes is some- ICP-MS. where between pure silver and pure copper electrodes. Differential pulse anodic stripping voltammetry (DPASV) Keywords Voltammetry . Solid electrodes . Real samples was used to measure zinc, cadmium and lead in ultrapure water only (18 MΩcm), and good linearity was found for all metals (r2=0.998) in the range of 0.5 to 5 ppb with a Introduction 600- to 1,200-s plating time. It was additionally found that cadmium and lead were better separated on the alloy Increasing focus on environmental surveillance [1, 2] has electrodes compared to pure silver electrodes. Measure- created a demand for continuous improvements and ments of nickel were carried out on alloy electrodes by use development of usable field instruments and sensors. of adsorptive differential pulse cathodic stripping voltam- Heavy metals represent an important group of contami- metry (Ad-DPCSV), and good linearity (r2=1.000) was nants, and monitoring of these species in the field is of found in the range from 0.5 to 5 ppb with an adsorption great importance to avoid serious environmental damage. time of 120 s. The alloy electrodes were also found to be Pollution by heavy metals, even in small concentrations, sensitive to nitrate, and good linearity (r2=0.997) was may have deadly influences on the surroundings [3–5]. − − found in the range from 1 mg L 1 to 100 mg L 1 using The most frequently used methods in environmental differential pulse voltammetry (DPV) scanning from monitoring today are atomic absorption spectroscopy −450 mV to −1,500 mV. Addition of nitrate in ultrapure (AAS) and inductively coupled plasma-mass spectroscopy water afforded two different peaks related to the successive (ICP-MS). However, in order to carry out continuous reductions of nitrate and nitrite. In ammonium buffer online monitoring, these methods are too complicated. Electrochemical techniques represent an alternative, fast- measuring and inexpensive group of methods useful for . * S. M. Skogvold Ø. Mikkelsen ( ) monitoring heavy metals. Different types of voltammetric Norwegian University of Science – and Technology Department of Chemistry, methods are particularly suitable [6 17], and voltammetric 7491 Trondheim, Norway apparatus for online monitoring of metal speciation can be e-mail: [email protected] constructed [18]. e-mail: [email protected] In order to succeed in making voltammetric field G. Billon . C. Garnier . L. Lesven . J.-F. Barthe apparatus for online monitoring of heavy metals, a critical University of Sciences and Technologies of Lille, factor is to develop usable electrodes. Liquid mercury Laboratory of Analytical and Marine Chemistry (UMR8013), represents the most frequently used material for electrodes 59655 Villeneuve d’Ascq, France in voltammetry; however, in field apparatus a liquid e-mail: [email protected] e-mail: [email protected] mercury electrode is difficult to install, and solid electrodes e-mail: [email protected] represent an easier alternative. Intensive research has been e-mail: [email protected] carried out in recent years in order to develop useful solid 1568 electrodes [18–27]. However, the main problems with solid silver and copper. Such alloys are noted for their good electrodes are lack of overpotential towards the hydrogen stability, serving as materials in jewellery for hundred of evolution reaction in water solutions, and problems with years. Furthermore, when alloying these metals, structural the stability over time due to adsorptions of organic or changes in the surface could improve the overvoltage charged compounds on the electrode surface or formation towards the hydrogen evolution reaction, something which of insulating oxide layers. is studied in this paper. Some practical applications of these A proper combination of chemical and electrochemical microelectrodes in real samples of polluted river water are cleaning may overcome the problem of passivation to also demonstrated. some extent, and increase the time between manual maintenance of the electrodes long enough to make it of potential use in the field [28, 29]. However, the problem Experimental with low overvoltage towards the hydrogen evolution reaction still has to be dealt with, since most solid metal Analyses were performed with voltammetric equipment electrodes actually have a relatively low overvoltage from PalmSens (The Netherlands) together with a three- towards hydrogen evolution. This makes them unsuitable electrode system using a platinum counter electrode, an for analyses of several important metals like nickel, Ag/AgCl/KCl (3 M) reference electrode, and silver–copper cobalt, zinc, iron and cadmium. Studies of specific mixed alloys were used as working quasi-microelectrodes (d = metal electrodes, containing two or more metals, have 80 μm). Additionally, as specified in the text below, some shown a significant increase in overvoltage towards analyses were performed with a homemade potentiostat. hydrogen evolution and are promising for use in field Oxygen was not removed from any of the samples. apparatus. Of specific interest are electrodes containing The silver alloys were ordered as wires from K. A. silver doped with one or more metals (e.g. mercury, Rasmussen, Hamar, Norway. The alloys tested were silver bismuth or copper) which have a high overvoltage 830 (83% silver and 17% copper) and silver 925 (92.5% towards the hydrogen evolution reaction [30–32]. silver and 7.5% copper). Additionally, pure silver wire Nitrate is another important compound to measure in (99.99%), ordered from Goodfellow Company (UK), was environmental monitoring, because of its important influ- used for making silver microelectrodes for comparative ence on the environment. Several papers have been measurements. The electrodes were made in a similar way published on the subject of fundamental processes to gold and silver microelectrodes described elsewhere associated with the reduction of nitrate with various [39], by gluing together 4–5 cm of the silver or silver metal substrates [48–56]. However, only a few papers alloy wires to a copper wire connector and then sealing focus on the analytical aspect, and the possibility of using the respective wires in polyethylene pipette tips (200 μL) voltammetric techniques with solid electrodes for determi- at 500 °C. A second tip enclosing the whole device was nation of nitrate in the environment [57–63]. Development finally stuck to the first one and fixed with non-con- of sensitive methods for measuring nitrate in the field is ductive epoxy glue. therefore of great interest and importance. The electrodes were first polished on P2,500 and Performing voltammetric analyses in the field also secondly on P4,000 (Struers) grid papers, before polishing requires a proper system for adding supporting electrolyte with diamond paste (1 μm, Struers). After polishing, the and stirring the solution. Even though it is possible to electrodes were checked with an optical microscope construct such a system, it should as easy as possible
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