Editorial
Frontiers in Electroanalytical Chemistry
E
lectroanalytical chemistry is a broad subject that today encompasses much more than electroanalysis. Research and development done by electroanalytical chemists encompasses electron transfer chemistry of enzymes and of organometallic reagents, corrosion and coatings, solar energy conversion, catalytic reactions in fuel cells, and membranebased separations. This diversity has developed over many years, and its growth continues. Electroanalytical chemistry also plays a large role in chemical analysis, particularly as embodied in ion-selective and enzyme electrodes. In this installment of my series of Frontiers in Analytical Chemistry editorials, I will point to some recent developments and opportunities in electroanalytical chemistry that seem especially exciting. Electroanalytical chemistry, along with other areas of analytical chemistry, has a strong theme of miniaturization. Thinking small is good, and the act of making electrodes smaller than the eye can see has significant consequences. Microelectrodes have pushed the electrochemical kinetics timescale into the nanosecond regime and have opened up possibilities for electroanalysis of polymer solids and surfaces. Microelectrodes have become pioneer tools in small-space analysis; voltammetric measurements in single neurons have been reported, as has the time-resolved analytical detection of individual vesicles releasing their neurotransmitter contents at cell walls. A new form of microscopy, scanning electrochemical microscopy, offers chemically sensitive images on micrometer scales. The ultimate diminution of electrode size or diffusion pathlength to values near molecular sizes promises a new and intimate view into interfacial chemistry fundamentals. A modified electrode topic experiencing rapid progress is that of oriented molecular monolayers. These monolayers will be important because they allow the environment of electron transfer reactions to be controlled and manipulated on molecular scales. There are further prospects with organized monolayers for design of artificial receptor sites and a new generation
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Analytical Chemistry, Vol. 66, No. 23, December 1, 1994
of chemical sensors. Again, note the small-dimension theme. The chemistry by which potentiometric responses can be evoked from ion-selective electrodes is rapidly expanding, so much so that I see them being referred to as species-selective electrodes because neutral molecular analytes are now targeted. These kinds of electrodes contribute mightily to all sorts of chemical analysis needs. Analyte selectivity is a major challenge in the world of sensors, and electroanalytical chemists are making fresh attacks on this problem by coupling redox enzymes with electrodes and by exploiting selective antigen-antibody binding reactions. There is a tremendous emphasis on glucose sensors, spurred by the relative sturdiness and consequent ease of use of the glucose oxidase enzyme as well as by the need for glucose sensors that can be used in clinical laboratories and by the individual diabetic patient for self-monitoring. Glucose sensor research combines clever schemes for glucose enzyme electrode electron transfer coupling with electrodes designed to be miniaturized, inexpensive and reliable to produce, and discarded after one measurement. I have always felt the diversity of electroanalytical research and application to be a great strength, because it forces quite broad interdisciplinary interactions of its participants with other kinds of chemists and even nonchemists. A a result, the field is anything but insular, and it continues to contain bright opportunities for applications in analytical and other areas of chemistry. Let's hear it for the electron pushers; they have a charged future.
P.S. I am grateful to a reader for pointing out that Vannevar Bush's report was presented to President Truman; President Roosevelt had passed away earlier in the spring of 1945. I'm glad to correct this factual error in last month's Editorial.
