current after a pulse should stabilize the improved response. In neither case is the mechanism of the improved performance well understood. Rather than altering the natural electroactive surface-solvent interface, one can modify the surface with "foreign molecules," as is well known. One example of this is the cobalt phthalocyanine modification t h a t has been shown to be effective in catalyzing a number of important reactions for detection (51, 52). A requirement of the electrode modification, when accomplished with molecules that are not native to the surface or the solvent, is that the modification be long lived. The friction from the flowing fluid in the detector and the chemistry of the environment will certainly conspire to limit the usefulness of most modified electrodes. Self-regenerating surfaces, protected surfaces, or thick overlayer-type modifications (such as ruthenium purple [53]) would seem to be the best.
Conclusion The development of electrochemical detectors parallels the development of the science of electrochemistry. The marvelous thing about research in this area is that electrochemistry is chemistry. Microstructural and chemical alterations of electrode surfaces can be made elegantly and precisely because
of the natural, and controllable, reactivity of the surface. More powerful detection techniques will be one result of this. The processes that occur at an electrode can be influenced by light, giving a new channel of selectivity to detection. Finally, it is worth noting that studies of noise have all demonstrated that the limiting factors in the lower limit of detection are the presence of Faradaic current from components of the system that are of no analytical interest, and instrumental noise. The fundamental limit has not been approached with an electrochemical detector. More selectivity and better sample preparation will improve the chemical environment problem, and perhaps some clever approaches to the instrumentation will solve the latter problem. References (1) Weber, S. G.; Purdy, W. C. Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 593. (2) Weber, S. G. In Detectors for Liquid Chromatography; Yeung, E. S., Ed.; Wiley Interscience: N e w York, 1986; p p . 229-91. (3) Stulik, K.; Pacâkovâ, Ν. Electroanalytical Measurements in Flowing Liquids; Ellis Harwood, Ltd.: Chichester, England, 1987, pp. 60-1. (4) Sioda, R. E.; Keating, Κ. Β. In Electroanalytical Chemistry; Bard, A. J., Ed.; Marcel Dekker: New York, 1982; Vol. 12, pp. 1-52. (5) Morgan, D. M.; Weber, S. G. Anal.
New from de Gruyter Photon Activation Analysis C h r i s t i a n S e g e b a d e , H a n s - P e t e r Weise, a n d G e o r g e J o h n Lutz 1988. viii + 705 pages. Illustrations. 17 χ 24 cm. ISBN 0-89925-305-9. Hardcover $193.00 This book provides an overview of the application of photonuclear reactions to activation analysis. It is intend ed to serve as both a source of general information on photon activation analysis and as a practical reference manual to accompany the analyst's laboratory work. Em phasis is placed upon experimentally obtained analytical, qualitative, and quantitative data. The results of the authors' laboratory work, as well as a large amount of literature data, are evaluated and presented as completely as possible. An elementary theoretical introduction is pro vided to assist those without a special knowledge of photonuclear physics. From the Contents Activation Analysis - the general principle · Photonuclear reactions · Activating radiation sources · Photon spec trometers · Properties and yields of radionuclides produced through photonuclear reactions · Analytical application · Bibliography · Subject Index price subject to change
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Chem. 1984, 56, 2560-67. (6) Berger, T . Abstracts of Papers, Pitts burgh Conference, Atlantic City, NJ; 1986; Abstract 1059. (7) Bezegh, Α.; Janata, J. Anal. Chem. 1987, 5.9, 494 A. (8) Box, G. E.; Hunter, W. G.; Hunter, J. S. Statistics for Experimenters; Wiley: New York, 1978; App. 3. (9) Weber, S. G. Presented at the Interna tional Electroanalytical Symposium, Chi cago, IL, 1985; paper 27. (10) Fosdick, L. E.; Anderson, J. L. Anal. Chem. 1986, 58, 2481. (11) Cope, D. K.; Tallman, D. E. J. Electroanal. Chem. 1986, 205, 101. (12) Roston, D. Α.; Shoup, R. E.; Kissinger, P. T. Anal. Chem. 1982,54,1417 A. (13) Matsuda, H. J. Electroanal. Chem. 1968,16, 153. (14) Lunte, C. E.; Shoup, R. E.; Kissinger, P . T. Anal. Chem. 1985, 57, 1541. (15) Chao, S.; Wrighton, M. S. J. Am. Chem. Soc. 1987,109, 2197. (16) O'Dea, J.; Osteryoung, J. Anal. Chem. 1980, 52, 2215. (17) Reardon, P . Α.; O'Brien, C. E.; Sturrock, P . E. Anal. Chim. Acta 1984, 162, 175. (18) White, J. G.; Jorgenson, J. W. Anal. Chem. 1986, 58, 2992. (19) White, J. G.; St. Claire, III, R. L.; Jor genson, J. W. Anal. Chem. 1986,58, 293. (20) Caudill, W. L.; Ewing, A. G.; Jones, S.; Wightman, R. M. Anal. Chem. 1983, 55, 1877. (21) Gunasingham, H.; T a y , B. T.; Ang, K. P . Anal. Chem. 1987,59, 262. (22) Last, T. A. Anal. Chem. 1983,55,1509. (23) Barnes, A. C ; Nieman, T. A. Anal. Chem. 1983,55, 2309. (24) Trubey, R. D.; Nieman, T . A. Anal. Chem. 1986, 58, 2549.
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