Basic atomic absorption spectroscopy

Atomic absorption spectroscopy of VPD solutions (VPD-AAS) and instrumental neutron activation analysis (INAA) offer similar detection limits for metallic impurities with silicon substrates. The main advantage of TXRF, compared to VPD-AAS, is its multielement capability AAS is a sequential technique that requires a specific lamp to detect each element. Furthermore, the problem of blank values is of little importance with TXRF because no handling of the analytical solution is involved. On the other hand, adequately sensitive detection of sodium is possible only by using VPD-AAS. INAA is basically a bulk analysis technique, while TXRF is sensitive only to the surface. In addition, TXRF is fast, with an typical analysis time of 1000 s turn-around times for INAA are on the order of weeks. Gallium arsenide surfaces can be analyzed neither by AAS nor by INAA. 

Li or a Li compound in the flame gives a bright crimson color due to its emission of670.8 nm photons produced by the short-lived species LiOH. This is the property that allows for the spectrophotometric determination of Li by atomic absorption spectroscopy (AAS) down to 20 ppb. Inductively-coupled plasma emission spectroscopy (ICPAES), inductively-coupled plasma mass spectroscopy (ICPMS), and ion chromatography (IC) improve this limit to about 0.1 ppb. A spot test for detection of Li down to 2 ppm is provided by basic KIO4 plus FeCl3. 

Figure 1.2 shows the basic instrumentation necessary for each technique. At this stage, we shall define the component where the atoms are produced and viewed as the atom cell. Much of what follows will explain what we mean by this term. In atomic emission spectroscopy, the atoms are excited in the atom cell also, but for atomic absorption and atomic fluorescence spectroscopy, an external light source is used to excite the ground-state atoms. In atomic absorption spectroscopy, the source is viewed directly and the attenuation of radiation measured. In atomic fluorescence spectroscopy, the source is not viewed directly, but the re-emittance of radiation is measured. 

One decade ago the term atomic absorption spectroscopy was familiar to only a small group of scientists, to a few chemists working on special problems, and to astrophysicists. Within the last few years, however, this analytical tedinique has found enthusiastic acceptance by science and industry. Several hundred papers have been published in a short time on basic research, instrumentation, development of methods, and practical application of atomic absorption spectroscopy. Several good reviews of the subject stressing various aspects have appeared (A13, D6, E2, G6, L3, L8, M6, M7, R2, R5, W15), and it seems hardly necessary to add to their number. The problems of medical laboratories and clinical... 

Describe the basic differences between atomic emission and atomic absorption spectroscopy. 

Part V covers spectroscopic methods of analysis. Basic material on the nature of light and its interaction with matter is presented in Chapter 24. Spectroscopic instruments and their components are described in Chapter 25. The various applications of molecular absorption spectrometric methods are covered in some detail in Chapter 26, while Chapter 27 is concerned with molecular fluorescence spectroscopy. Chapter 28 discusses various atomic spectrometric methods, including atomic mass spectrometry, plasma emission spectrometry, and atomic absorption spectroscopy. 

Figure 11.9 Basic principle of atomic absorption spectroscopy - the lock and key effect. From Dean, J. R., Atomic Absorption and Plasma Spectroscopy, ACOL Series, 2nd Edn, Wiley, Chichester, UK, 1997. Reproduced with permission of the University of Greenwich.

In 1955 Walsh established the foundations of modern analytical atomic absorption spectroscopy. In the same year Alkemade and Milatz also published a paper suggesting similar procedures. The work of Walsh, however, was much more detailed, since he examined the theory of the method, the basic principles involved, the instrumentation requirements, and its advantages over flame emission. 

This textbook is an outgrowth of the author s experience in teaching a course, primarily to graduate students in chemistry, that included the subject matter presented in this book. The increasing use and importance of atomic spectroscopy as an analytical tool are quite evident to anyone involved in elemental analysis. A number of books are available that may be considered treatises in the various fields that use atomic spectra for analytical purposes. These include areas such as arc-spark emission spectroscopy, flame emission spectroscopy, and atomic absorption spectroscopy. Other books are available that can be catalogued as methods books. Most of these books serve well the purpose for which they were written but are not well adapted to serve as basic textbooks in their fields. 

The concentration of inorganic components in forage crops varies according to crop maturity, temperature, and soil pH and composition. The analyses of mineral content can reveal soil or management deficiencies as well as optimum harvest time for proper crop management. Actual mineral analyses are used to determine the amount of mineral supplementation to be added to an animal ration for proper nutritional balance. Reference methods of analysis include inductively coupled argon plasma (ICP), atomic absorption spectroscopy (AAS), and x-ray fluorescence spectroscopy (XRF). These techniques are well established for the analysis of mineral elements in whole-plant material. The exact procedures for sample preparation and analysis are well documented. Copies of the procedures may be obtained from instrument manufacturers or are readily found using basic texts for each analytical technique. 

Atomic absorption spectroscopy has become one of the most frequently used tools in analytical chemistry. This is because for the determination of most metals and metalloids the technique offers sufficient sensitivity for many applications and is relatively interference free. There are two basic atom cells (a means of turning the sample, usually a liquid, into free atoms) used in atomic absorption spectroscopy ... 

Absorption spectroscopy records depletion by the sample of radiant energy from a continuous or frequency-tunable source, at resonance frequencies that are characteristic of various energy levels ia atoms or molecules. The basic law of absorption, credited to Bouguer-Lambert-Beer, states that ia terms of the iacident, Jq, and transmitted, light iatensities, the absorbance, M (or transmittance, T), is given by equation 1 ... 

An introductory manual that explains the basic concepts of chemistry behind scientific analytical techniques and that reviews their application to archaeology. It explains key terminology, outlines the procedures to be followed in order to produce good data, and describes the function of the basic instrumentation required to carry out those procedures. The manual contains chapters on the basic chemistry and physics necessary to understand the techniques used in analytical chemistry, with more detailed chapters on atomic absorption, inductively coupled plasma emission spectroscopy, neutron activation analysis, X-ray fluorescence, electron microscopy, infrared and Raman spectroscopy, and mass spectrometry. Each chapter describes the operation of the instruments, some hints on the practicalities, and a review of the application of the technique to archaeology, including some case studies. With guides to further reading on the topic, it is an essential tool for practitioners, researchers, and advanced students alike. 

Atomic spectroscopy as a means of detection in gas chromatography is becoming popular because it offers the possible selective detection of a variety of metals, organometallic compounds, and selected elements. The basic approaches to GC-atomic spectroscopy detection include plasma emission, atomic absorption, and fluorescence. 

X-ray absorption spectroscopy is a powerful tool for nanoparticle analysis due to its selectivity and independence of sample physical state. It is limited in range to the region within about 0.5-0.7 nm of a particular (chosen) absorber atom in the structure, but can be applied to amorphous or even liquid samples. The basic theory behind the origins and analysis of the extended X-ray absorption fine structure (EXAFS) has been well described by Sayers et al. (1970, 1971) and Lee et al. (1981). with mineralogical applications detailed by Brown et al. (1988). The crucial aspect of the EXAFS spectrum is that it is formed by an electron backscattering process in the vicinity of the absorber... 

In this chapter, we discuss the basic principles that are necessary to understand measurements made with electromagnetic radiation, particularly those deeding with the absorption of UV, visible, and IR radiation. The nature of electromagnetic radiation and its interactions with matter are stressed. The next four chapters are devoted to. spectroscopic instruments (Chapter 25), molecular absorption spectroscopy (Chapter 26), molecular fluorescence spectroscopy (Chapter 27), and atomic spectroscopy (Chapter 28). 

With the exception of better optical resolution needed, the basic instrument used for atomic emission is very similar to that used for atomic absorption with the difference that no primary light source is used for atomic emission. One of the most critical components for this technique is the atomisation source because it must also provide sufficient energy to excite the atoms as well as atomise them. The earliest energy sources for excitation were simple flames, but these often lacked sufficient thermal energy to be truly effective sources. The development in 1963 and the introduction in 1970 of the first commercial inductively coupled plasma (ICP) as a source for atomic emission dramatically changed the use and the utility of emission spectroscopy (Thompson Walsh 1983). 

CONTENTS 1. Basic Principles (J. W. Robinson). 2. Instrumental Requirements and Optimisation (J. E. Cantle). 3. Practical Techniques (J. E. Cantle). 4a. Water and Effluents (B. J. Farey and L A. Nelson). 4b. Marine Analysis by AAS (H. Haraguchi and K. Fuwa). 4c. Analysis of Airborne Particles in the Workplace and Ambient Atmospheres (T.J. Kneip and M. T. Kleinman). 4d. Application of AAS to the Analysis of Foodstuffs (M. Ihnat). 4e. Applications of AAS in Ferrous Metallurgy (K. Ohis and D. Sommer). 4f. The Analysis of Non-ferrous Metals by AAS (F.J. Bano). 4g. Atomic Absorption Methods in Applied Geochemistry (M. Thompson and S. J. Wood). 4h. Applications of AAS in the Petroleum Industry W. C. Campbell). 4i. Methods forthe Analysis of Glasses and Ceramics by Atomic Spectroscopy (W. M. Wise et al.). 4j. Clinical Applications of Flame Techniques (B.E. Walker). 4k. Elemental Analysis of Body Fluids and Tissues by Electrothermal Atomisation and AAS (H. T. Delves). 4I. Forensic Science (U. Dale). 4m. Fine, Industrial and Other Chemicals. Subject Index. (All chapters begin with an Introduction and end with References.)... 

This book is intended to fill the aforementioned gap and to present the basic principles and instrumentation involved in analytical atomic spectroscopy. To meet this objective, the book includes an elementary treatment of the origin of atomic spectra, the instrumentation and accessory equipment used in atomic spectroscopy, and the principles involved in arc-spark emission, flame emission, atomic absorption, and atomic fluorescence. 

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