Atomic absorption spectroscopy evaluation

Particle composition is far more difficult to evaluate. Bulk elemental analysis [atomic absorption spectroscopy (AA) or inductively coupled plasma mass spectrometry (ICP-MS) are most common for metals] is useful in confirming the overall bimetallic composition of the sample, but provides no information regarding individual particles. Microscopy techniques, particularly Energy Dispersive Spectroscopy (EDS), has supported the assertion that bimetallic DENs are bimetallic nanoparticles, rather than a physical mixture of monometallics [16]. Provided the particle density is low... 

Me tals and metallic compounds are among the toxic substances most often found in workplace environments (1,2), Industrial hygienists and hygiene chemists must accurately determine the presence and amount of toxic metals and their compounds in the industrial environment. Accurate methods for the quantification of metals in biological and atmospheric samples are required for the industrial hygienist to properly evaluate the environment. Atomic absorption spectroscopy (AAS) has been the primary method of analysis for toxic metals because AAS is sensitive, specific, and rapid especially compared to colorimetric analysis. 

R4. Rann, C. S., Evaluation of a flame as the spectral source in atomic absorption spectroscopy. Speclrochim. Ada, Part B 23, 245-256 (1968). 

The differential pulse and square wave techniques are among the most sensitive means for the direct evaluation of concentrations, and they find wide use for trace analysis. When they can be applied, they are often far more sensitive than molecular or atomic absorption spectroscopy or most chromatographic approaches. In addition, they can provide information about the chemical form in which an analyte appears. Oxidation states can be defined, complexation can often be detected, and acid-base chemistry can be characterized. This information is frequently overlooked in competing methods. The chief weakness of pulse analysis, common to most electroanalytical techniques, is a limited ability to resolve complex systems. Moreover, analysis time can be fairly long, particularly if deaeration is required. 

Freeh. W.. Cedergren, A., Cederberg, C. and Vessman, J. (1982). Evaluation of some critical factors affecting determination of aluminum in blood, plasma or serum by electrothermal atomic absorption spectroscopy. Clin. Chem., 28, 2259. 

Kirkbright. G.F.. Chuan. S.H. and Snook. R.D. (1980) An evaluation of some matrix modification procedures for the use in determination of mercury and selenium by atomic absorption spectroscopy with a graphite tube electrothermal atomizer. Atom. Spec-trosc.. 1. 85-89. 

Atomic fluorescence is the most recent development in analytical atomic spectroscopy thus it has not had time to be evaluated as well as other techniques. Further developments in this field with respect to optimizing sources and sample cells, together with improvements in instrumental parameters and development of readily available commercial instrumentation, should lead to this technique serving in the area of analytical spectral methods to supplement the already well-established arc and spark emission, flame emission, and atomic absorption spectroscopy. 

FIGURE 10-37. Calibration curves of atomic absorption signals of zinc using absorbance and percentage absorption versus zinc concentration in /ig/ml. [From W. G. Schrenk, Evaluation of Data, in Flame Emission and Atomic Absorption Spectroscopy, Vol. 2, Edited by J. A. Dean and T. C. Rains, Marcel Dekker, New York (1971), Chap. 12. Used by permission of Marcel Dekker, Inc.]... 

Welz B and Schubert-Jacobs M (1991) Evaluation of a flow injection system and optimization of parameters for hydride generation atomic absorption spectroscopy. Atomic Spectroscopy 12 91-104. 

The most common method of analytical determination of rubidium is atomic absorption spectroscopy (AAS) or neutron activation analysis (NAA). Chemical methods of analysis for the determination of rubidium are difficult because of the tedious procedures required to effect the separation from the other alkali metals. The beneficial effects of the addition of other alkali metals, particularly potassium, sodium, and cesium, added to interfere with the ionization of rubidium is detailed by many authors [39,53-55]. Recent evaluation of the benefits of these ions in the determination of rubidium in human erythrocytes has concluded that erythrocytes should be diluted 1 50 with potassium to give a final potassium concentration of 10000 ppm. Under these conditions, the sensitivity of absorbance was increased about threefold and rubidium concentrations could be determined in the range 0-60 ppm [56]. 

The mercury removal performance of pilot-scale ICDAC and of Norit s FGD carbon were determined in a 0.236 m% (0.25 MWe) pilot plant operated by CONSOL, Inc., Library, PA. The pilot plant can simulate flue gas conditions downstream of the air preheater in a coal fired utility power plant. The flue gas mercury concentration studied (10-15 pg/m ) is typical of utility flue gas concentration. Mercury removals were evaluated in the flue gas duct, which provided a gas residence time of approximately 2 seconds, and in the baghouse, where the solids retention times can be as long as 30 min. Common test conditions were flue gas flow, 0.165 m /s flue gas wet bulb temperature, 50-53°C flue gas composition, 1000 ppmv dry SO2, 10 vol% dry O2, and 10 vol% dry CO2. All tests were conducted with a fly ash obtained from a coal-fired utility boiler firing an eastern bituminous coal. The fly ash feed rate was 4.5 kg/hr (solids loading of 90.6-104.7 gm/dcm ). Mercury removal was determined from the mercury feed rate, the solids (carbon and fly ash) feed rate, and mercury analysis of the feed and recovered solids (by combustion followed by cold vapor atomic absorption spectroscopy). Except where noted, all mercury removal results discussed in this paper include mercury removal by the carbon sorbent and the fly ash. A more detailed description of the pilot test unit is given elsewhere (27]. 

Low-temperature, photoaggregation techniques employing ultraviolet-visible absorption spectroscopy have also been used to evaluate extinction coefficients relative to silver atoms for diatomic and triatomic silver in Ar and Kr matrices at 10-12 K 149). Such data are of fundamental importance in quantitative studies of the chemistry and photochemistry of metal-atom clusters and in the analysis of metal-atom recombination-kinetics. In essence, simple, mass-balance considerations in a photoaggregation experiment lead to the following expression, which relates the decrease in an atomic absorption to increases in diatomic and triatomic absorptions in terms of the appropriate extinction coefficients. 

The evaluation of ionization potentials by spectroscopic methods (adiabatic IA), yields very accurate values. This amounts to identifying an appropriate Rydberg series in the absorption spectroscopy of complex atoms or molecules. The excitations leading to Rydberg-like series may be expressed as... 

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