Polarography automated

The way in which automation of electroanalysis can be achieved depends very much on the specific requirements of the application. In order to illustrate this we have selected a number of typical examples. However, in doing so, we did not consider normal automation inherent to the nature of the analytical method, e.g., automatic scanning of the voltammetric curve in polarography and other voltammetric techniques, in addition to many additional refinements within these methods such as those treated already in Chapter 3 therefore, the selection of the examples in this chapter cannot be other than arbitrary, where the borderline between the common and the uncommon in the future certainly will shift towards the former. 

Amperometric titrations have an even wider range of application than polarography. Although the titrant may be added from a burette, in many applications it is electrically generated in a coulometric cell (p. 261). Such an arrangement lends itself to complete automation and is particularly valuable for the titration of very small quantities. For examples of coulometric titrations with amperometric equivalence point detection see Table 6.5. 

GLC, atomic absorption and mass spectrophotometry, enzymatic, and specific colorimetric procedures seem to be the likely candidates for routine use in the future. Automation will certainly be common. GLC is now used to detect imitation muscat wines (127). Characteristic flavor byproducts of yeasts may be detected and measured. Multiple correlation of the amounts of the more influential major and minor constituents with wine quality is the goal of such research. A simple apparatus for the simultaneous determination of the redox potential (two platinum electrodes), pH, specific conductivity, oxygen, and carbon dioxide (ion-specific electrode) has been devised (128). Molecular oxygen in wines has been determined by several procedures—polarography (129) and GLC being the latest. 

Electrochemical methods of analysis have grown greatly in application and importance over the last 40 years, and this has been largely due to the development and improvement of electronic systems permitting refinements in the measurement of the critical characteristics mentioned in the foregoing. In addition to this, the measurement systems and the advanced electronics now permit much of the work in electroanalytical chemistry to be automated and controlled by microprocessors or computers. Some electroanalytical techniques have become very widely accepted others, such as polarography/voltammetry, less so. This has been due to early problems with equipment. Despite the fact... 

More unusual ideas involve the flow of solution through tubular electrodes or the use of so called wall jet electrodes in which a rapid jet of solution is impinged directly onto a small electrode. Since these methods involve flow of solution through tubing rather than an open cell, they introduce the possibility of automated analysis. The samples could be automatically injected into a continuous flow of fresh supporting electrolyte - flow injection analysis. Conventional polarography does not lend itself as easily to automation as does this version of stripping voltammetry. 

In practice, electrochemistry not only provides a means of elemental and molecular analysis, but also can be used to acquire information about equilibria, kinetics, and reaction mechanisms from research using polarography, amperometry, conductometric analysis, and potentiometry. The analytical calculation is usually based on the determination of current or voltage or on the resistance developed in a cell under conditions such that these are dependent on the concentration of the species under study. Electrochemical measurements are easy to automate because they are electrical signals. The equipment is often far less expensive than spectroscopy instrumentation. Electrochemical techniques are also commonly used as detectors for LC, as discussed in Chapter 13. 

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