Downloaded by 80.82.77.83 on March 3, 2018 | https://pubs.acs.org Publication Date: December 9, 1987 | doi: 10.1021/bk-1988-0361.pr001
Preface CHEMICAL MEASUREMENTS ARE CHARACTERIZED by three fundamental processes: detection, identification, and quantification. The first of these relates to the ultimate measurement capability as expressed in the detection limit. The invitation to organize a symposium on this topic carried the suggestion that we address the "true meaning" of detection limits. That charge, in fact, influenced the structure of the symposium and the content of this volume. The objective of this book, therefore, is primarily to explore, from both fundamental and practical perspectives, the meaning of detection in chemical measurement science. It is not intended to serve as a compendium of the current "detection limits" for a broad range of analytical methods. The "meaning" of detection and detection limits has been examined in two senses: (I) the basic scientific meaning as to exactly what is signified by the minimum detectable quantity of a chemical substance, and how that quantity is derived; and (2) the meaningfulness or usefulness of such detection limits in the context of external problems, such as those affecting society, industrial processes, or scientific research. It is timely and appropriate for these two sides of detection to be considered together, for the ability to detect prescribed amounts of chemical substances in the natural environment, foods, or manufactured products can have important effects on our economic or physical well-being. However, unless the technical significance of detection decisions and detection limits is fully defined, misleading or even dangerous conclusions can follow. Equally important is mutual understanding by the lay public and the technical community of their respective interpretations of detection. This text consists of an overview chapter and four principal sections. The first section addresses the issue of detection from the perspective of the well-informed but nonscientific public, that is, the most extensive user community of detection limits. The authors of Chapters 2 and 3, a former member of Congress and a former congressional subcommittee staff director, respectively, are eminently qualified to present the public view because they have both helped to shape that view and because they respond to the publics technological needs. The second section begins with a tutorial chapter, followed by six contributions treating fundamental characteristics of the chemical measurement process, which must be taken into account to derive meaningful detection limits. Included in this section
vn Currie; Detection in Analytical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
Downloaded by 80.82.77.83 on March 3, 2018 | https://pubs.acs.org Publication Date: December 9, 1987 | doi: 10.1021/bk-1988-0361.pr001
are expositions on comparative detection limits, a matter of some importance in selecting chemical methods or in interpreting interlaboratory data. Five chapters make up the third section of the book. Selected examples illustrate the care and energy involved in devising methods of extreme sensitivity. Exhaustive method characterization and attention to a host of potential sources of error mark these contributions. These chapters, together with several chapters in the preceding section, also treat important areas of application. The text concludes with two panel discussions. The first reflects the overall focus of the book, in that it examines with some vigor "real-world" problems and needs for meaningful detection, both in the laboratory and in the regulatory environment. The second panel, comprising members of an international team working on coding environmental analytical data, shares some of the approaches and issues involved in preparing low-level chemical data for computerized data bases. Opportunities for information loss or distortion are quite significant in this regard because of problems of rounding and truncation and interpretation of the meaning of detection. The objectives of this book will have been met if improved communication on the subject of detection results. Such communication would be beneficial not only between the public and the technical community, but also within the technical community. As indicated in the overview chapter, the history of detection limits in analytical chemistry has been marked by an unfortunate degree of diversity in terminology and meaning and a lack of attention to the probabilities of both false negatives and false positives. At the same time, we should help the public understand that all detection limits must allow for these two types of error, and that "zero" detection limits cannot, in principle, be attained. DISCLAIMER This book was edited by Lloyd A. Currie in his private capacity. No official support or endorsement by the National Bureau of Standards is intended or should be inferred. L L O Y D A. CURRIE
Gaithersburg, MD 20899 September 1, 1987
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Currie; Detection in Analytical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
