Atomic fluorescence analytical procedures

The choice between X-ray fluorescence and the two other methods will be guided by the concentration levels and by the duration of the analytical procedure X-ray fluorescence is usually less sensitive than atomic absorption, but, at least for petroleum products, it requires less preparation after obtaining the calibration curve. Table 2.4 shows the detectable limits and accuracies of the three methods given above for the most commonly analyzed metals in petroleum products. For atomic absorption and plasma, the figures are given for analysis in an organic medium without mineralization. 

The formation of relatively stable fluorescent products by the reaction of adrenaline with ethylenediamine (and certain other primary amines) in air, first reported in 1948 by Natelson et was adapted by Weil-Malherbe and Bone in 1952 for the assay of catecholamines.197 198 Since 1952 much work, largely of an empirical nature, has been carried out to improve the analytical procedure since often apparently minor variations of the reaction conditions have a significant effect on the fluorescence observed (see Section V, E, 4). Paper chromatographic examination of the reaction mixtures obtained from adrenaline and noradrenaline suggested that more than one product could be formed in each case.199-205 The main fluorescent product of the interaction of adrenochrome (1) (obtained by oxidation of adrenaline) and ethylenediamine in air has been obtained as a crystalline solid by Harley-Mason and Laird and shown to be 2,3-dihydro-3-hydroxy-l-methylpyrrolo[4,5-g]quinoxaline (94) (7% yield).206,207 This compound has two hydrogen atoms less than... 

TJecent interest in the trace element content of coal has increased the need for rapid and accurate analytical methods for their determination. Because x-ray fluorescence analysis has demonstrated its usefulness in determining major, minor, and trace elements in numerous other types of materials, it was felt that this method could be extended to trace element determinations in whole coal. In the past, such analyses were seriously hampered by the lack of standard samples. However, research being conducted in our laboratories under the sponsorship of the U. S. Environmental Protection Agency produced a large number of coal samples for which trace elements had been determined by two or more independent analytical procedures, for example, optical emission, neutron activation, atomic absorption, and wet chemical methods. These coals were used as standards to develop an x-ray fluorescence method that would determine many trace and minor elements in pressed whole coal samples. 

All raw and treated coals were analyzed at Ames Laboratory for trace, major, and minor elements using energy-dispersive x-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and atomic absorption spectrophotometry (AA). General analytical procedures employed for each of these techniques are discussed separately below. 

Emphasis was therefore put on analytical procedures able to determine many elements in parallel and/or requiring almost no previous separation. procedures preferred were X-ray fluorescence using a Am source and Si(Li)-detector, atomic absorption spectrophotometry, gamma spectrometry using tracer isotopes and Ge(Li)-detector and acid-base titrations with recording of the pH-volume derivative. Table 2 summarises the use of these methods for the different elements, and it also gives a rough indication of interferences, sensitivity and accuracy obtained. 

A mong the preferred analytical methods for determining mercury con-centrations in natural samples save been closed system reduction-aeration procedures using mercury detection by gas phase atomic absorption or atomic fluorescence spectrophotometry (I-I5). In studies in the oceanic regime, where the amount of mercury in a liter sample of open-ocean seawater can be as small as 10 ng (11,15,16,17), a. pre-concentration stage may be required. The lowered detection limits which accompany a preliminary concentration step are most desirable when the sample materials are rare or in limited quantities such as carefully collected open-ocean biota, open-ocean rain water, and deep-ocean seawater. 

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. 

X-ray fluorescence is a spectroscopic technique of analysis, based on the fluorescence of atoms in the X-ray domain, to provide qualitative or quantitative information on the elemental composition of a sample. Excitation of the atoms is achieved by an X-ray beam or by bombardment with particles such as electrons. The universality of this phenomenon, the speed with which the measurements can be obtained and the potential to examine most materials without preparation all contribute to the success of this analytical method, which does not destroy the sample. However, the calibration procedure for X-ray fluorescence is a delicate operation. 

Radiochemical methods of analysis are considerably more sensitive than other chemical methods. Most spectral methods can quantitate at the parts-per-mil-lion (ppm) level, whereas atomic absorption and some HPLC methods with UV, fluorescence, and electrochemical methods can quantitate at the parts-per-billion (ppb) levels. By controlling the specific activity levels, it is possible to attain quantitation levels lower than ppb levels of elements by radiochemical analyses. Radiochemical analysis, inmost cases, can be done without separation of the analyte. Radionuclides are identified based on the characteristic decay and the energy of the particles as described in detection procedures presented above. Radiochemical methods of analysis include tracer methods, activation analysis, and radioimmunoassay techniques. 

Nickel and vanadium along with iron and sodium (from the brine) are the major metallic constituents of crude oil. These metals can be determined by atomic absorption spectrophotometric methods (ASTM D-5863, IP 285, IP 288, IP 465), wavelength-dispersive X-ray fluorescence spectrometry (IP 433), and inductively coupled plasma emission spectrometry (ICPES). Several other analytical methods are available for the routine determination of trace elements in crude oU, some of which allow direct aspiration of the samples (diluted in a solvent) instead of time-consuming sample preparation procedures such as wet ashing (acid decomposition) or flame or dry ashing (removal of volatile/combustible constituents) (ASTM D-5863). Among the techniques used for trace element determinations are conductivity (IP 265), flameless and flame atomic absorption (AA) spectropho-... 

As any method of anion analysis may be applied if isolation techniques such as evaporation, precipitation, ion exchange, or solvent extraction are employed, we shall limit the discussion to direct methods and admit isolation techniques only if they are simple and rapid. The methods apparently best suited to the direct analysis of trace amounts of anions therefore are limited to selective membrane potentiometric, atomic absorption, fluorescence, and spectrophotometric methods following oxidation-reduction or complexometric reactions, or solvent extraction. Most of the traditional analytical methods—gravimetric, titrimetric, emission spectrometric, and electrical methods involving oxidation and reduction are less suitable, as are most radioactive procedures including neutron activation analysis, except in special cases. 

Batch mode can be performed in membranes and in powdered solids. The simplest procedures use the solid phase as a medium to support the analytes and carry out the measurement. Among membranes, a variety of cellulosic supports have been used, and the nature of the analyte plays an important role in producing luminescence. Polar or ionic molecules give off a strong adsorption interaction due to hydrogen bonding and induce intense phosphorescent signals, while nonpolar compounds produce weak dispersion interactions and small shifts in fluorescence spectra and weak phosphorescence. External heavy-atom perturbation can be used to induce... 

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. 

The most common procedures for analyzing cadmium concentrations in blood and urine are inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS). Furthermore, electrochemical methods, neutron activation analysis (NAA) and X-ray fluorescence spectrometry (XRF) can be applied. Several factors influence the choice of the analytical method, e.g. the matrix and the detection limit required. 

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