Electrochemical electroanalysis

Elektroanalyse, /. electroanalysis, elektroaoalytisch, a. electroaualytical, Elektro-chemie, /. electrochemistry, -chemi-ker, m. electrochemist. elektrochemisch, a. electrochemical, Elektroden-abstand, m. distance between electrodes, -kohle, /. electrode carbon, elektrodenlos, a, electrodeless, without electrodes. 

Conducting polymers have found applications in a wide variety of areas,44 45 and many more have been proposed. From an electrochemical perspective, the most important applications46 appear to be in batteries and supercapacitors 47,48 electroanalysis and sensors49-51 electrocatalysis,12,1, 52 display and electrochromic devices,46 and electromechanical actuators.53... 

Apart from the study of physicochemical aspects such as ion solvation, and bio-mimetic aspects such as photosynthesis or carrier-mediated ion transfer (Volkov et al., 1996, 1998), there are several areas of potential applications of electrochemical IBTILE measurements comprising electroanalysis, lipophilicity assessment of drugs, phase transfer catalysis, electro-assisted extraction, and electrocatalysis. 

In electroanalysis, the techniques are pre-eminently based on processes that take place when two separate poles, the so-called electrodes, are in contact with a liquid electrolyte, which usually is a solution of the substance to be analysed, the analyte. By means of electrometry, i.e., by measuring the electrochemical phenomena occurring or intentionally generated, one obtains signals from which chemical-analytical data can be derived through calibration. Often electrometry (e.g., potentiometry) is applied in order to follow a reaction that goes to completion (e.g., a titration), which essentially represents a stoichiometric method, so that the electrometry merely acts as an end-point indicator of the reaction (which means a potentiometric titration). The electrochemical phenomena in electroanalysis, whether they take place in the solution or at the electrodes, are often complicated and their explanation requires a systematic treatment of electroanalysis. 

Modification of electrodes by electroactive polymers has several practical applications. The mediated electron transfer to solution species can be used in electrocatalysis (e.g. oxygen reduction) or electrochemical synthesis. For electroanalysis, preconcentration of analysed species in an ion-exchange film may remarkably increase the sensitivity (cf. Section 2.6.4). Various... 

Sljukic B, Bank CE, Compton RG (2005) Exploration of stable sonoelectrocatalysis for the electrochemical reduction of oxygen. Electroanalysis 17 1025-1034... 

Zanoni MVB, Stradiotto NR (2005) Electrochemical behaviour of aromatic amines protected by nitrobenzenesulfonyl group. Electroanalysis 7(4) 365-369... 

F. Bedioui, S. Trevin, and J. Devynck, Chemically modified microelectrodes designed for the electrochemical determination of nitric oxide in biological systems. Electroanalysis 8, 1085-1091 (1996). 

M. Stoytcheva, Electrochemical evaluation of the kinetic parameters of a heterogeneous enzyme reaction in presence of metal ions. Electroanalysis 14, 923-927 (2002). 

H. Suzuki, Advances in the microfabrication of electrochemical sensors and systems. Electroanalysis 12, 703-715 (2000). 

M. Akram, M.C. Stuart, and D.K.Y. Wong, Signal generation at an electrochemical immunosensor via the direct oxidation of an electroactive label. Electroanalysis 18, 237-246 (2006). 

J. Min and A.J. Baeumner, Characterization and optimization of interdigitated ultramicroelectrode arrays as electrochemical biosensor transducers. Electroanalysis 16, 724—729 (2004). 

L. Mao, J. Jin, L. Song, K. Yamamoto, and L. Jin, Electrochemical microsensor for in vivo measurements of oxygen based on Nafion and methylviologen modified carbon fiber microelectrode. Electroanalysis. 11, 499-504 (1999). 

A. Eftekhari, Electrochemical properties of lanthanum hexacyanoferrate particles immobilized onto electrode surface by Au-codeposition method. Electroanalysis 16, 1324 (2004). 

J.M. Zen, A.S. Kumar, and H.W. Chen, Electrochemical behavior of stable cinder/Prussian blue analogue and its mediated nitrite oxidation. Electroanalysis 13, 1171-1178 (2001). 

G.C. Fiaccabrino and M. Koudelka-Hep, Thin-film microfabrication of electrochemical transducers. Electroanalysis 10, 217-222 (1998). 

J. Wang, Carbon-nanotube based electrochemical biosensors a review. Electroanalysis 17, 7-14 (2005). 

Q. Zhao, Z. Gan, and Q. Zhuang, Electrochemical sensors based on carbon nanotubes. Electroanalysis 14, 1609-1613 (2002). 

J.H.T. Luong, S. Hrapovic, D. Wang, F. Bensebaa, and B. Simard, Solubilization of multiwall carbon nanotubes by 3-aminopropyltriethoxysilane towards the fabrication of electrochemical biosensors with promoted electron transfer. Electroanalysis 16, 132-139 (2004). 

K. Kerman, Y. Morita, Y. Takamura, M. Ozsoz, and E. Tamiya, DNA-directed attachment of carbon nanotubes for the enhanced electrochemical label-free detection of DNA hybridization. Electroanalysis 16,1667-1672 (2004). 

Huang, H., et ah, Fabrication of new magnetic nanoparticles (Fe304) grafted multiwall carbon nanotubes and heterocyclic compound modified electrode for electrochemical sensor. Electroanalysis, 2010. 22(4) p. 433-438. 

For the purposes of this book, the term electroanalysis will be taken to mean the analysis of an analyte by using electrochemical methods. The analyte will be termed the electroactive species (or material). Sometimes, however, we will also call it the electroanalyte. At heart, analysts working with electrochemical techniques monitor the behaviour of an electroactive species by performing two types of experiment they will either measure a potential (or occasionally variations in potential), or they will measure the charges, Q, and changes in the charge, AQ. 

Electroanalysis is a powerful means of obtaining solubility constants for solutes in which the amount of one or more of the ions can be determined electrochemically. To obtain a(ion), we will either employ an ISE or perform a calculation with the Nemst equation. 

In Chapter 1, we saw that electrochemistry is the branch of chemistry employed by an analyst when performing electroanalytical measurements, while in Chapter 2, we saw that electrochemical measurements fall within two broad categories, namely determination of a potential at zero current, and determination of a current, usually by careful variation of an applied potential. These two branches of electroanalysis are bridged in this present chapter by showing - on an elementary level - why char ge flows, and also explaining how an analyst can interpret and thus process quantitative data during charge flow. 

In electroanalysis, the area is conventionally considered to have units of cm. If the electrode is fractal (see Section 5.1.2 and Figure 5.5), then the electrochemical area, rather than the geometric area, is employed as A . 

Trojanowicz, M., Electrochemical Detectors in Automated Analytical Systems , in Modem Techniques in Electroanalysis, Vanysek P. (Ed.), Wiley-Interscience, New York, 1996, pp. 187-239. This chapter contains a fairly thorough discussion of the possible arrangements of electrodes within flow systems, and for a variety of applications. 

Electrochemical Methods (Bard and Faulkner), Instrumental Methods in Electrochemistry ( The Southampton Electrochemistry Book ) (Greef et al.) and Modem Techniques in Electroanalysis (Van sek), all cited above, present suitable simulation programs. 

Hitchman, M. L. and Hill, H. A. O., Electroanalysis and electrochemical sensors . Chemistry in Britain, 22, 1117-1124 (1986), provides a lively, general introduction to this subject, giving details of sensors based on potentiometry, such as ISEs, together with some historical background. 

In general, the electrochemical performance of carbon materials is basically determined by the electronic properties, and given its interfacial character, by the surface structure and surface chemistry (i.e. surface terminal functional groups or adsorption processes) [1,2]. Such features will affect the electrode kinetics, potential limits, background currents and the interaction with molecules in solution [2]. From the point of view of electroanalysis, the remarkable benefits of CNT-modified electrodes have been widely praised, including low detection limits, increased sensitivity, decreased overpotentials and resistance to surface fouling [5, 9, 11, 17]. 

M. Tagliazucchi and E.J. Calvo present another important and exciting means of modification by electrochemically active polyelectrolytes. Polyelectrolytes modify surfaces by their inherent electric charges, which can be used, e.g., for constructing multilayer films of opposite charge, or simply by changing the electrochemical potential of reaction partners. Their role in many areas of chemistry, particularly of electroanalysis and biochemistry, cannot be overemphasized. 

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