Atomic absorption spectroscopy discussion

Detector Detection in FIA may be accomplished using many of the electrochemical and optical detectors used in ITPLC. These detectors were discussed in Chapter 12 and are not considered further in this section. In addition, FIA detectors also have been designed around the use of ion-selective electrodes and atomic absorption spectroscopy. 

Discussion. Because of the specific nature of atomic absorption spectroscopy (AAS) as a measuring technique, non-selective reagents such as ammonium pyrollidine dithiocarbamate (APDC) may be used for the liquid-liquid extraction of metal ions. Complexes formed with APDC are soluble in a number of ketones such as methyl isobutyl ketone which is a recommended solvent for use in atomic absorption and allows a concentration factor of ten times. The experiment described illustrates the use of APDC as a general extracting reagent for heavy metal ions. 

It is impossible in the present volume for the determination of a wide range of elements by atomic absorption spectroscopy to be discussed in detail. A few... 

Also in the literature, there is little discussion of the accuracy or reproducibility of the analytical technique used for determining the corresponding matrix and particle composition [37, 38], Various analytical methods that have been used to determine the particle concentration in the deposit include gravimetric analysis [29, 31, 39], x-ray fluorescence [5], atomic absorption spectroscopy [33, 40, 41-43], and micro-... 

In the present work, emphasis is placed on summarizing recent applications of atomic absorption spectroscopy for the analysis of biological and medicinal materials. Reports prior to mid 1967 are discussed in detail elsewhere 2 3)... 

Of particular concern in this analysis is sodium because it destroys soil structure, is associated with increased soil pH, and can be toxic to plants. Sodium can easily be determined by atomic absorption spectroscopy (AAS), flame ionization spectroscopy (FIS), and inductively coupled plasma (ICP) methods. Soil structure is discussed in Chapter 2 and the various spectroscopic methods discussed in Chapter 14. 

The following three important aspects of atomic absorption spectroscopy shall be discussed here briefly, namely ... 

For the purpose of the following discussion, the xenobiotics studied in the dogfish shark were divided into three classes 1) those relatively hydrophilic (Table V) those relatively lipophilic (i.e., solubility in water less than 1 mg/ml, Table VI) and, 3) metal-containing pollutants (Table VII) Most of these data have been previously reported (18-23) using C compound, for assay, with the exception of sodium lauryl sulfate (SLS) ( S), cis-Pt (atomic absorption spectroscopy) and phenol red (spectrophotometry). Unless otherwise stated these data are presented as total radioactivity and the hazards of doing so are recognized (24). 

Analytical. Arsenic oxidation state determinations were per-formed by hydride generation-flame atomic absorption spectroscopy (AAS) at the University of Arizona Analytical Center. The analytical procedures are discussed in Brown, et al. (12). 

It is now up to the analyst to interpret the dendrogram with respect to the possible causes of the structures found. For example in the case at hand a discussion with the laboratories revealed that laboratory E optimized its determination of some elements by atomic absorption spectroscopy. If we inspect the raw data in Tab. 5-2. the special location of the... 

In the following subsections the application of atomic absorption spectroscopy to the determination of the more important elements of biological and clinical interest is presented, and special problems and interferences encountered with individual elements are discussed in detail. The resonance lines given at the beginning of each subsection are those showing greatest absorption, although many elements possess several resonance lines that can be used in analysis. The sensitivity limits quoted are the lowest reported in the literature, usually defined as that concentration of the test element in aqueous solution which produces 1% absorption. The reproducibility of results by most atomic absorption techniques lies... 

In addition to the continuum sources just discussed, line sources are also important for use in the UV/visible region. Low-pressure mercury arc lamps are very common sources that are used in liquid chromatography detectors. The dominant line emitted by these sources is the 253.7-nm Hg line. Hollow-cathode lamps are also common line sources that are specifically used for atomic absorption spectroscopy, as discussed in Chapter 28. Lasers (see Feature 25-1) have also been used in molecular and atomic spectroscopy, both for single-wavelength and for scanning applications. Tunable dye lasers can be scanned over wavelength ranges of several hundred nanometers when more than one dye is used. 

For detailed discussions of electrothermal atomizers, see B. E. Erickson. Anal. Chem., 2000, 72, 543A Electrothermal Atomization for Anahtical Atomic Spectrometry. K. W. Jackson, Ed. New York Wiley, 1999 D. J. Buther and J. Sneddon. A Practical Guide to Graphite Furnace Atomic Absorption Spectrometry. New York Wiley. 1998 C. W. Fuller, Electrothermal Atomization for Atomic Absorption Spectroscopy. London The Chemical Society. 1978. 

Flame atomic absorption spectroscopy (AAS) is currently the most widely used of all the atomic methods listed in Table 28-1 because of its simplicity, effectiveness, and relatively low cost. The technique was introduced in 1955 by Walsh in Australia and by Alkemade and Milatz in Holland. The first commercial atomic absorption (AA) spectrometer was introduced in 1959, and use of the technique grew explosively after that. Atomic absorption methods were not widely used until that time because of problems created by the very narrow widths of atomic absorption lines, as discussed in Section 28A-1. 

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. 

Speciation of organometallic compounds containing Au and Ag, on the other hand, was paid only scant attention as a subject for analytical research. The analytical methods that supported research on these compounds had to be dug out from the experimental sections of articles dealing with diverse aspects of chemistry, physics, biochemistry, etc. A review appeared on some of the antiinflammatory drugs shown in Table 1, discussing determination of Au in body fluids and pharmaceutical preparations, and speciation of the compounds and their metabolites. The methods included varieties of atomic absorption spectroscopy (AAS), varieties of neutron activation analysis (NAA), inductively coupled plasma spectrometry combined with mass spectrometric detection (ICP-MS),... 

The measurement of total calcium in a biological sample can be made by any method sensitive only to the element and not to its particular chemical form. Atomic absorption spectroscopy is excellent as such a method. Obviously, the spatial resolution that can be obtained with this method is limited, and it is hard to imagine its application to elemental mapping of single cells. The techniques discussed in this subsection have been limited to those that permit a spatial resolution of at least 1 u.m on samples usually prepared by sectioning the frozen biological specimens. 

Sources that emit a few discrete lines find wide use in atomic absorption spectroscopy, atomic and molecular fluorescence spectroscopy, artd Raman spectroscopy (refractomeiry and polarimciry also u.se line sources). The familiar mercury and sodium vapor lamps provide a relatively few sharp lines in the ultraviolet and visible regions and are used in several spectroscopic instruments. I loilow-cathodc lamps and clectrodelcss discharge lamps are the most important line sourcc.s for atomic absorption and fluorescence methods. Discussion of such sources is deferred to Section 9H- . 

Several elements (Zn, Pb, Cuy Ni, Ca, Mg, Fe, and Mn) are determined routinely in water samples using atomic absorption spectroscopy. Sodium and potassium are determined by flame emission. The preparation of the samples the analytical methody the detection limits and the analytical precisions are presented. The analytical precision is calculated on the basis of a sizable amount of statistical data and exemplifies the effect on the analytical determination of such factors as the hollow cathode sourcey the ffamey and the detection system. The changes in precision and limit of detection with recent developments in sources and burners are discussed. A precision of 3 to 5% standard deviation is attainable with the Hetco total consumption and the Perkin-Elmer laminar flow burners. 

Each element has a unique set of permitted electronic energy levels because of its unique electronic structure. The wavelengths of light absorbed or emitted by atoms of an element are characteristic of that element. The absorption of radiant energy by atoms forms the basis of AAS, discussed in Chapter 6. The absorption of energy and the subsequent emission of radiant energy by excited atoms form the basis of AES and atomic fluorescence spectroscopy, discussed in Chapter 7. 

The comparison of detection limits Is a fundamental part of many decision-making processes for the analytical chemist. Despite numerous efforts to standardize methodology for the calculation and reporting of detection limits, there is still a wide divergence In the way they appear in the literature. This paper discusses valid and invalid methods to calculate, report, and compare detection limits using atomic spectroscopic techniques. Noises which limit detection are discussed for analytical methods such as plasma emission spectroscopy, atomic absorption spectroscopy and laser excited atomic fluorescence spectroscopy. 

Atomic emission spectroscopy (AES) and atomic absorption spectroscopy (AAS) are In a manner similar to our discussion of molecular spectroscopy, where we compared UV absorption with UV excitation and subsequent fluorescence, these two determinative approaches are the principal ways to identify and quantitate trace concentration levels of metal contamination in the environment. As the need developed to quantitate increasing numbers of chemical elements in the Periodic Table, so too came advances in instrumentation that enabled this to be achieved at lower and lower IDLs AES and AAS techniques are both complementary and competitive. Atomic fluorescence spectroscopy (AFS) is a third approach to trace metal analysis. However, instrumentation for this has not as yet become widespread in environmental testing labs and it is unlikely that one would see atomic or what has become useful x-ray atomic fluorescence spectroscopy. Outside of a brief mention of the configuration for AFS, we will not cover it here. 

The energy required to produce spectral emission can be provided in several ways, including discharge tubes, flames, electric arcs, electric sparks, plasmas, and lasers. The first two, discharge tubes and flames, are not discussed here. Flames are treated in Chapter 9 (Flame Emission Spectroscopy) and discharge tubes are discussed in Chapter 10 (Atomic Absorption Spectroscopy). 

The spectral response of a photomultiplier tube varies with the coating materials used on the photocathode. Spectral responses of various photomultiplier tubes are given in Table 6-3. Chapter 6 also includes a general discussion of photomultiplier phototubes. The 1P28 tube (S-5 response) is sensitive from 2000 to 6500 A and is frequently used for atomic absorption spectroscopy. The Hamamatsu R106 also has an S-5 response but uses a silica window to lower the usable short wavelength response to about 1700 A. The S-20 response of the RCA 4459 permits measurements to 8500 A and is very useful for most of the alkali metals. 

Sodium diethyldithiocarbamate (DDTC) was used to separate transition metal cation with a CTAB micellar phase and a CIS column [32]. The limits of detection obtained with atomic absorption spectroscopy were in the tens of picograms injected. Since a high concentration of i-propanol (45% v/v) was added to the 0.03 M CTAB mobile phase, the presence of micelles may be discussed. Simple ion-pairing between CTAB and the DDTC metal species may explain the observed selectivity. Tartaric acid was also used as a ligand for transition metal cations with a SDS micellar mobile phase and a CIS column [33]. 

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