Electroanalytical instruments

The manufacturers of electroanalytical instrumentation cannot always immediately satisfy the experimenter s requirements, but often this can be remedied by instrumental development in mutual contact. An illustrative example is the construction of the carbon-fibre microelectrodes (MFC) by... 

In 1976, Radiometer61 presented for the first time a microprocessor-controlled titration system. Since then, the microprocessor has been used preferentially and as a fully integrated part (in line) in electroanalytical instruments as a replacement for the on-line microcomputer used before. Bos62 gave a comprehensive description of the set-up and newer developments with microprocessors in relation to microcomputers and indicated what they can do in laboratory automation. Many manufacturers are now offering versatile microprocessor-controlled titrators such as the Mettler DL 40 and DL 40 RC MemoTitrators, the Metrohm E 636 Titroprocessor and the Radiometer MTS 800 multi-titration system. Since Mettler were the first to introduce microprocessor-controlled titrators with their Model DK 25, which could be extended to a fully automated series analysis via the ST 80/ST 801 sample transport and lift together with the CT 21/CT211 identification system, we shall pay most attention to the new Mettler MemoTitrators, followed by additional remarks on the Metrohm and Radiometer apparatus. 

Let us dwell on Figure 6.4 for a moment. The standards and sample solutions are introduced to the instrument in a variety of ways. In the case of a pH meter and other electroanalytical instruments, the tips of one or two probes are immersed in the solution. In the case of an automatic digital Abbe refractometer (Chapter 15), a small quantity of the solution is placed on a prism at the bottom of a sample well inside the instrument. In an ordinary spectrophotometer (Chapters 7 and 8), the solution is held in a round (like a test tube) or square container called a cuvette, which fits in a holder inside the instrument. In an atomic absorption spectrophotometer (Chapter 9), or in instruments utilizing an autosampler, the solution is sucked or aspirated into the instrument from an external container. In a chromatograph (Chapters 12 and 13), the solution is injected into the instrument with the use of a small-volume syringe. Once inside, or otherwise in contact with the instrument, the instrument is designed to act on the solution. We now address the processes that occur inside the instrument in order to produce the electrical signal that is seen at the readout. 

At this writing it is possible to link digital instrumentation with notebook computers and even achieve portability. Developments have been so rapid in this area that it is difficult to imagine what will come next. General-purpose processor-based electroanalytical instruments are now available from Amel, Bioanalytical Systems, Cypress Systems, EcoChemie, Metrohm, Tacussel, and Princeton Applied Research. 

Instrumentation for selected aspects of electroanalytical chemistry is covered in Chapters 6-8. Although computers have made a tremendous impact on electroanalytical instrumentation, many aspects of these chapters are timeless. The basic configurations of a potentiostat have not changed since the early 1960s, although the electronic components themselves are dramatically different Learn to build your own potentiostat in Chapter 6, then see how to fine-tune it in Chapter 7. 

The reference electrode contributes heavily to the economics of electroanalytical chemistry. Companies that sell and service electroanalytical instrumentation are few in number and small in size, or they are parts of much larger companies. One supplier of electroanalytical instrumentation is Princeton Applied Research Corp. (PARC) of Princeton, Newjersey. PARC is a subsidiary of EG G Instruments, Inc. Among the many suppliers of ion-selective electrodes are Orion (Boston, Massachusetts), Coming (Coming, New York), and Ingold (Wilmington, Massachusetts). Brinkmann Instruments, Inc. (Westbury, New York) is a useful supplier of titration equipment. 

A detection system This consists of a flow cell located in the optical or electroanalytical instrument. Single-channel (for the determination of one analyte) or multichannel configuration (for several analytes) can be used. 

Although this has been known since the very beginning of electrochemistry in the nineteenth century, commercial electroanalytical instrumentation has been available only for the past 35 years. The direct reduction of 02 in aqueous solutions (especially biological and water treatment and sewage samples) is... 

A wide variety of multipurpose electroanalytical instruments are available, several of which include provision for both controlled current and controlled potential operation (Bl). Automatic titrators record the potential against the volume of titrant, and in some a greater accuracy is possible by using derivative curves obtained with an associated circuit. 

A resurgence of interest in electroanalytical techniques during the past several years has been described by Flato (38) as a Renaissance. For some time, developments of other techniques, particularly atomic absorption spectroscopy, coupled with the non-availability of commercial instrumentation, had caused a deterioration of interest in the practical applications of electroanalysis. However, rapid advances in electronic technology have now resulted in the commercial availability of sophisticated, versatile, reliable, yet relatively inexpensive electroanalytical instrumentation which is easy to operate. 

This chapter deals with the latest developments and state of the art In the automation of electroanalytical Instrumentation as a logical reeult of the Intrinsic characteristics of each technique and the potential offered by tech-... 

Economou, A.S., Bolis, S.D., Efstathiou, C.E., Volikakis, G.J., 2002. A virtual electroanalytical instrument for square wave voltammetry. Anal. Chim. Acta 467, 179—188. 

Square-wave voltammetry (SWV) is one of the four major voltammetric techniques provided by modern computer-controlled electroanalytical instruments, such as Autolab and pAutolab (both EcoChemie, Utrecht), BAS 100 A (Bioana-lytical Systems) and PAR Model 384 B (Princeton Applied Research) [1], The other three important techniques are single scan and cyclic staircase, pulse and differential pulse voltammetry (see Chap. II.2). All four are either directly applied or after a preconcentration to record the stripping process. The application of SWV boomed in the last decade, firstly because of the widespread use of the instruments mentioned above, secondly because of a well-developed theory, and finally, and most importantly, because of its high sensitivity to surface-confined electrode reactions. Adsorptive stripping SWV is the best electroanalytical method for the determination of electroactive organic molecules that are adsorbed on the electrode surface [2]. 

Spirit rovers) included mainly X-ray spectrometers and imagers. It was not until 2007 with the launch of the Phoenix Mars lander mission that the first electroan-alytical measurement system was delivered to the martian surface. Here we present the historical context of the first electroanalyses on Mars, an overall description of the electrochemically based sensors that were part of the Phoenix Wet Chemistry Laboratory (WCL), the results of the martian soil analyses and their implications, the most recent Earth-based experiments, and a preview of the next-generation electroanalytical instruments currently in development for upcoming missions to Mars and beyond. 

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