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480 Pages·1983·7.709 MB·English
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Related Pergamon Titles of Interest BOOKS Earlier Volumes in the Pergamon Series in Analytical Chemistry Volume 1 MEITES: An Introduction to Chemical Equilibrium and Kinetics Volume 2 PATAKI & ZAPP: Basic Analytical Chemistry Volume 3 YINON & ZITRIN: The Analysis of Explosives Volume 4 JEFFERY & HUTCHISON: Chemical Methods of Rock Analysis, 3rd Edition Volume 5 PRIBIL: Applied Complexometry OTHER BOOKS BOUMANS: Line Coincidence Tables for Inductively Coupled Plasma Atomic Emission Spectrometry (2 volume set) CHALMERS: Microprocessors in Analytical Chemistry SAATY & ALEXANDER: Thinking with Models JOURNALS Computer Languages Computers & Chemistry Information Systems Talanta Full details of all Pergamon publications/free specimen copy of any Pergamon journal available on request from your nearest Pergamon Office. Computers in Analytical Chemistry by PHILIP G. BARKER, FBCS, FRSC Principal Lecturer in Computer Science, Teesside Polytechnic Sometime Lecturer in Computing, University of Durham Sometime SRC Research Fellow, Department of Chemistry (Swansea), University of Wales PERGAMON PRESS OXFORD • NEW YORK • TORONTO • SYDNEY • PARIS • FRANKFUF U.K. Pergamon Press Ltd., Headington Hill Hall, Oxford 0X3 OBW, England U.S.A. Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York 10523, U.S.A. CANADA Pergamon Press Canada Ltd., Suite 104, 150 Consumers Rd., Willowdale, Ontario M2J 1P9, Canada AUSTRALIA Pergamon Press (Aust.) Pty. Ltd., P.O. Box 544, Potts Point, N.S.W. 2011, Australia FRANCE Pergamon Press SARL, 24 rue des Ecoles, 75240 Paris, Cedex 05, France FEDERAL REPUBLIC Pergamon Press GmbH, Hammerweg 6, OF GERMANY D-6242 Kronberg-Taunus, Federal Republic of Germany Copyright © 1983 Philip G. Barker All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers. First edition 1983 Reprinted 1984 Library of Congress Cataloging in Publication Data Barker, Philip G. Computers in analytical chemistry. (Pergamon series in analytical chemistry ; v. 6) Includes bibliographical references and indexes. I. Chemistry, Analytic—Data processing. I. Title. II. Series. QD75.4.E4B37 1983 543'.0028'54 82-22276 British Library Cataloguing in Publication Data Barker, Philip G. Computers in analytical chemistry—(Pergamon series in analytical chemistry; 6) 1. Chemistry, and analytical —Data processing I. Title 543'.0028'5 QD75.4.E4 ISBN 0-08-024008-9 In order to make this volume available as economically and as rapidly as possible the author's typescript has been reproduced in its original form. This method unfortunately has its typographical limitations but it is hoped that they in no way distract the reader. Printed in Great Britain by A. Wheaton & Co. Ltd., Exeter To God Science and Humanity Organisation of the Book Chemical analysis and analytical chemistry are domains of scientific endeavour that are fundamental tSo many areas of applied science and technology. Taken together these subjects form a mass of knowledge which has its own structure and subdivisions, theories and folklore, experts, practitioners and manufacturing technology. Analytical chemistry thus covers an extremely complex web of human activity. During the last century Society has experienced many changes in technology that have affected everybody's way of life - particularly the scientist and the way in which scientific chemical analysis is undertaken. Moreover, the last ten to fifteen years has seen the rapid growth of computer technology. This too is slowly having its impact on analytical chemistry in a variety of ways ranging from large scale automation through to laboratory machines 1 that show some degree of''intelligence. It is the intention of this book to cover some of the ways in which computers are used in analytical chemistry - the latter term being interpreted in its widest sense. An understanding or background of chemistry/analytical chemistry is assumed. Because of the all-pervasive nature of the subject an attempt is made in Chapter One to answer the question, 'What is Analytical Chemistry?. It does this by looking at some application areas in which analysis forms a fundamental part of the day to day activity of those involved in its practice. For the purpose of illustration, some techniques of analysis are described in considerable detail. Obviously, the space devoted to this chapter does not enable it to be comprehensive. Hopefully, though, it will at least be representative of what happens in a wide variety of analytical chemistry laboratories - if not in academia, then, at least, in the commercial and industrial worlds. In Chapter Two the author tries to formulate the basic steps involved in the analytical process. Various illustrations are used to describe how a computer system might assist the analyst in the sometimes formidable task of analysing an unknown material. Here, fact occasionally turns to fancy when a description is given of some of the ways in which computers may be used in the not too distant future. On this front, some of the important applications include the use of industrial robots, the use of sophisti- cated mathematical modelling and simulation techniques, the creation of large data bases and the application of artificial intelligence concepts to the design of computer programs known as 'expert systems'. This chapter also describes the influences that recent developments in computer input and output devices are having on the way in which the analyst is able to record and display the results of his/her work. Chapter Three is devoted to a cursory study of some of the instruments that are currently being used by analysts throughout a wide variety of laboratories. It pays particular attention to those instruments that for one reason or another require the application of computer technology. As early as 1964 Joshua Lederberger at Stanford University was probably one of the first to pioneer the use of real-time computer systems within the laboratory environment. Since this early work, which was devoted to mass spectral analysis, many significant advances have taken place. Nowadays there are five important application areas of computers within analytical instrumentation: (1) data acquisition, (2) data processing and enhance- ment, (3) storage and retrieval of data, (4) automatic interpretation of results, and (5) control uses. After presenting a simple model for a typical analytical instrument and outlining some of its important vii viii Organisation of the Book properties this chapter discusses some of the applications of computers in three of the most important analytical methods: gas chromatography, infrared and mass spectrometry. Obviously, many of the general principles outlined in the specific examples chosen apply to a much wider range of instrumentation. The chapter concludes with a description of how smaller analytical units such as GC, IR, MS can be linked together to form more 'sophisticated* instruments. Any form of technical description of computers is delayed until Chapter Four. Here a description of small computer systems (microprocessors and microcomputers), medium sized computers (minicomputers) and large computers (mainframes and super-computers) is presented. The chapter introduces the concepts of computer hardware and software. The archi- tecture of a simple integrated circuit (or 'chip') is discussed in the context of its being the building block for larger systems. Examples of minicomputer, mainframe and super-computer systems are also briefly outlined. Control applications are an important facet of the computer. Equally important - perhaps, more so - is its ablility to store and retrieve data. In Chapter Five, the concepts of data collection (or data acquisition) are discussed. Theoretical considerations relevant to sampling theory are outlined and techniques for storing analogue and digital data are briefly described. A summary of the various types of storage device, such as magnetic tape and disks, is also given in this section. The inter-connection of instruments - both to each other and to computer hardware - is a major area of interest within all branches of analytical chemistry. Consequently, Chapter Six is devoted to the topic of interfacing. Although the main emphasis is on electrical interfacing, other forms are briefly outlined. Various types of standard electrical and electronic interfaces such as the IEEE-488, CAMAC and S-100 are described. In addition, some of the problems associated with the design, implementation and use of non-standard interfaces are mentioned. In Chapter Seven, as a natural follow-on from interfacing, the author turns his attention to the basic types of communication channel that are necessary to enable instrument/computer inter-connection and the flow of data between one device and another. Several different types of communi- cation link are discussed - couriers, wired links, optical fibres, infrared data links, microwaves and satellite systems. Fundamental to present day data communication are the world*s telecommunication net- works. Consequently, in view of its importance, this chapter contains a brief section devoted to basic telecommunications; the basic principles of communication networks are introduced in order to provide the necessary background for a later chapter on computer networks. Because of the need to ensure the privacy of data and information that is transmitted over the available communication links, the chapter concludes with a short discussion of data encryption. Progress in electronics, computing and precision engineering have made possible significant advances in automation. Chemistry, in particular applied analytical chemistry, has been unable to avoid the onward march of this new area of technology. Automatic analysis is now a rapidly growing sector of chemical science. Because of its importance, Chapter Eight is devoted to a study of the application of automation to various aspects of laboratory analysis. Several approaches are considered including the use Organisation of the Book ix of in-house development teams and the purchase or lease of turnkey packages. A brief overview of the future potential role of the analyst within this area is then given. Chapter Nine deals with various aspects of data processing. Most of the activities that take place in the laboratory produce data in one form or another. Before information can be derived from experimental or analytical measurements, the raw data obtained in the laboratory (or on site) has to be processed by methods that are appropriate to the investi- gation concerned. Several different approaches to computerised data processing are outlined. The chapter discusses both numeric and non- numeric techniques as well as some of the more advanced applications such as pattern recognition, modelling and optimisation. The storage of experimental results and other important information in computer based systems requires the design and implementation of appro- priate storage mechanisms. Computer data bases are often used to provide the required facilities. In view of their growing importance, Chapter Ten is used to present an introduction to this topic. Because of the existing large volume and continual high growth rate of information that is of relevance to analytical science - both its literature and scientific results - the need for computerised information services is of vital importance. Such services provide a variety of computer based (or generated) tools to enable the analytical scientist to gain access to and, hence, make use of the valuable work of other scientists. The wide range of tools are grouped together under the title of 'information services' and are described in Chapter Eleven. Many large companies have geographically dispersed laboratories, processing plants and administrative centres. The sharing of data, information and control is of vital importance, as is the general coordi- nation of an organisation's activity. Because of the growing interest in the use of distributed communication systems for achieving these goals the final chapter of the book is devoted to a study of computer networks. Various types of system are described: local area, national and inter- national networks. The fundamental modes of operation of these systems are outlined and likely future directions of development summarised. CAC - A* Acknowledgements I would like to express my sincere thanks to Professor D. Betteridge for suggesting that this work should be undertaken. I am also indebted to the University of Durham and Teesside Polytechnic for providing many of the resources that enabled much of the background research to be undertaken. Mr. Peter Henn and the staff of Pergamon Press contributed invaluable help and advice. To all those who have helped me with the preparation of this book I am deeply grateful. xi 1 What is Analysis? INTRODUCTION Chemistry is one of the oldest sciences known to Mankind. Introductory text books on the subject often describe its domain as: the science of the properties of elementary and compound substances and the nature of the laws that describe how these combine together and react one with another. Chemistry is thus concerned with a wide range of topics. It deals with the everyday objects and events that take place around us and with the more esoteric entities and happenings on distant planets, in flames, in ionization chambers and within the human body. It is concerned with the discovery and manufacture of new materials (food, fuel, plastics, clothes - to mention just a few) and the safety of the environment in which we live - land, sea, river and the atmosphere. Above all it is a well documented, progressive science that offers an exciting intellectual framework for those wishing to embark upon its more detailed study. For a variety of reasons, most people at some stage in their lives become acquainted with the subject or with one or other of its multifarious applications. Children often encounter the subject for the first time at school - as one of the many options contained in an over-laden science curriculum. Others gain their knowledge as a result of some less formal interest - assaying the alcohol content of a wine they have been fermenting; trying to ascertain why the soil in their garden will not sustain the growth of roses; or, by means of a suitable dye, attempting to restore the colour of a garment whose attractiveness has faded with old age. Once kindled, an interest in chemistry is often difficult to extinguish. Consequently, for a large number of people chemistry becomes a professional discipline that forms the basis of a life long career. Those who undertake a deeper, more involved, study of the subject do so as a consequence of several possible factors. Some are motivated by the financial rewards of their employment as professional chemists. Many others are endowed with an insatiable desire to discover new knowledge and cherish the accolades that this can bring. However, there are also those who have a less professional interest and who treat the subject as a hobby - just like stamp collecting, bird watching or painting. These are the 1 2 Computers in Analytical Chemistry amateur chemists, of whom there are a great number. No matter how their fundamental motivations may differ, those who pursue the discipline of chemistry have much in common. This common ground undoubtedly embraces: (a) an understanding of the basic principles of science and its application to the bringing together of cause and effect; (b) some knowledge of engineering principles and a desire to build things - the chemist often constructs molecules, theories, experimental rigs and measuring apparatus; and, (c) a working knowledge of the basic ideas inherent in design - of synthetic pathways, of equipment and of analytical techniques. Like other scientists, perhaps, the most fundamental attribute that chemists have in common is that of being an observer. In this context the feature that distinguishes the chemist from other scientists lies in the nature of the systems that are dealt with and the types of observations that are made. Fundamental to chemistry - indeed, to all branches of science - are the basic principles involved in the 'analytical method* (Ber68). Using this approach a scientist sets about enumerating those factors which influence a particular situation or state of affairs. An attempt is then made to measure in a quantitative way the influences of the forces or factors that are deemed to be important within the confines of the system that has been chosen for investigation. All scientists are thus primarily concerned with observations made on some particular, carefully selected, system. Because of its subsequent importance, the concept of a system needs to be more firmly established. In the broadest possible sense such an entity may be defined as: a set of objects together with relationships between the objects and between their attributes (Wei75) For the chemist, the objects of interest will be atoms and molecules. The relationships will be the numerous laws that define how these entities interact and react together. The attributes will be the various properties that the atoms and molecules themselves possess. Such was the definition of chemistry that might have been promoted years ago. Today t however, it is much more than this. Nowadays the definition of chemistry and the scope of chemical systems must include the very process of life and the mechanisms of living. The relationships mentioned above must be extended to include a study of the ways in which atoms and molecules (and their properties) affect people and other living species - if only roses in an undernourished garden. Provided one accepts the importance of gaining a knowledge of the relationships and attributes that dominate a chemical system one must also accept the need for appropriate methods to enable these to be elucidated and recorded. Most often these objectives are realised through 1 controlled' experiments that incorporate proven measuring techniques that form the basis of the scientist's interest in analytical chemistry. However, despite the longevity of chemistry itself, it is only in relatively recent times that chemical analysis has gained the hallmarks of a precise and sophisticated science. Indeed, fewer than 100 years ago its deficiencies were a cause for public scandal (Cam79). As time progresses new measuring tools become available which are capable of providing the scientist with previously unknown measuring capabilities.

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