Other elemental analyses

A number of other common elements can be analysed using similar principles to the C, H and N analysis. In fact the only element which is not easily determined is oxygen — the oxygen content is usually inferred as a residual mass from the quantities of the other elements. 

The sulfur in organic and biological materials is determined by burning in a stream of oxygen. The SO2 produced is reacted with hydrogen peroxide to form sulfuric acid, which can then be titrated  

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Weak gold anomalies and trends are present, typically associated with areas of hydrothermal breccias and alteration. Of the other elements analysed, As shows the best contrast with values ranging from 2-2800 ppm. 

In Eggborough power plant it was found that Zn, Pb, Mo, Cu and As are concentrated in the fly ash compared with the bottom ash, whereas for the other trace elements studied (Ba, Cr, Nb, Rb, Sr, V, Y, Zr) there was very little fractionation (Martinez-Tarazona Spears 1996, tables 3 and 4). Mass balance calculations show that for the elements studied only S and As are depleted in the combustion ashes and all the other elements analysed appear to have been retained. Not included within the analyses were Hg, Cl, and F, and loss of these elements would be anticipated based on their volatility (Sloss Davidson 2001). 

Since the 1950s XRF has been used extensively for the analysis of solids, powders, and liquids. The technique was extended to analyze thin-film materials in the 1970s. XRF can be used routinely for the simultaneous determination of elemental composition and thickness of thin films. The technique is nondesuuctive, rapid, precise, and potentially very accurate. The results are in good agreement with other elemental analysis techniques including wet chemical, electron-beam excitation techniques, etc. 

Physical and chemical interferences elevate the XRF analysis detection limits for certain soil types, the actual detection limits may exceed these for an interference-free matrix shown in Table 3.10. The XFR detection limits are always higher than the detection limits for other elemental analysis techniques. The high detection limits may not be appropriate for some types of DQOs and are the greatest limitation of XRF screening. 

Dybczynski, R., Veglia, A., Suschny, O. Milk powder (A-11) A new IAEA reference material for trace and other element analysis. In Bratter, P., Schramel, P. (eds.) Trace Element Analytical Chemistry in Medicine and Biology, pp. 657-674. de Gruyter, New York (1980)... 

One of the most important pieces of information required to elucidate the molecular structure of an unknown organic compound is its molecular mass, which provides a window within which the elemental composition and the final structure of the compound must fit. Therefore, the first essential step to identifying a compound is to measure its molecular mass by determining the m/z value of the molecular ion. Molecular mass measurements can be performed at either low or high resolution. A low-resolution measmement provides information about the nominal mass of the analyte, and its elemental composition can be also determined for low-molecular-weight compounds from the isotopic pattern. From a high-resolution mass spectrum, the accurate molecular mass can be determined, from which it is also feasible to deduce the elemental composition. Chemists who work with synthetic compounds and natural products rely heavily on the exact mass measurement data for structmal assignment. This value is acceptable in lieu of the combustion or other elemental analysis data. An acceptable value of the measured mass should be within 5 ppm of the accmate mass [1]. As shown below, the mass measurement error is reported either in parts per million (ppm) or in millimass units (mmu). 

This procedure is thus properly called an X-ray fluorescence, or X-ray emission method. X-ray fluorescence (XRF) is a powerful tool for rapid, quantitative determinations of all but the lightest elements. In addition, XRF is used for the qualitative identification of elements having atomic numbers greater that of oxygen (>8) and is often used for semiquantitative or quantitative elemental analyses. A particular advantage of XRF is that it is nondestructive, in contrast to most other elemental analysis techniques. 

Although distillation and elemental analysis of the fractions provide a good evaluation of the qualities of a crude oil, they are nevertheless insufficient. Indeed, the numerous uses of petroleum demand a detailed molecular analysis. This is true for all distillation fractions, certain crude oils being valued essentially for their light fractions used in motor fuels, others because they make quality lubricating oils and still others because they make excellent base stocks for paving asphalt. 

X-Ray Methods. In x-ray fluorescence the sample containing mercury is exposed to a high iatensity x-ray beam which causes the mercury and other elements ia the sample to emit characteristic x-rays. The iatensity of the emitted beam is directly proportional to the elemental concentration ia the sample (22). Mercury content below 1 ppm can be detected by this method. X-ray diffraction analysis is ordinarily used for the quaUtative but not the quantitative determination of mercury. 

Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

Only slightly less accurate ( 0.3—0.5%) and more versatile in scale are other titration techniques. Plutonium maybe oxidized in aqueous solution to PuO " 2 using AgO, and then reduced to Pu" " by a known excess of Fe", which is back-titrated with Ce" ". Pu" " may be titrated complexometricaHy with EDTA and a colorimetric indicator such as Arsenazo(I), even in the presence of a large excess of UO " 2- Solution spectrophotometry (Figs. 4 and 5) can be utilized if the plutonium oxidation state is known or controlled. The spectrophotometric method is very sensitive if a colored complex such as Arsenazo(III) is used. Analytically usehil absorption maxima and molar absorption coefficients ( s) are given in Table 10. Laser photoacoustic spectroscopy has been developed for both elemental analysis and speciation (oxidation state) at concentrations of lO " — 10 M (118). Chemical extraction can also be used to enhance this technique. 

The filler metal is analyzed for those specific elements for which values are shown. If the presence of other elements is indicated in the analysis, the amount of those elements is deterrnined to ensure that the maximum for each is <0.05 wt% and the maximum total of other elements is <0.15 wt%. Remainder of material is Al. 

The detection of impurities or surface layers (e.g., oxides) on thick specimens is a special situation. Although the X-ray production and absorption assumptions used for thin specimens apply, the X-ray spectra are complicated by the background and characteristic X rays generated in the thick specimen. Consequently, the absolute detection limits are not as good as those given above for thin specimens. However, the detection limits compare very favorably with other surface analysis techniques, and the results can be quantified easily. To date there has not been any systematic study of the detection limits for elements on surfaces however, representative studies have shown that detectable surface concentrations for carbon and... 

The LIMS technique is rarely used for quantitative elemental analysis, since other techniques such as EPMA, AES or SIMS are usually more accurate. The limitations of LIMS in this respect can be ascribed to the lack of a generally valid model to describe ion production from solids under very brief laser irradiation. Dynamic range limitations in the LIMS detection systems are also present, and will be discussed below. 

Another application involves the measurement of copper via the radioisotope Cu (12.6-hour half-life). Since Cu decays by electron capture to Ni ( Cu Ni), a necessary consequence is the emission of X rays from Ni at 7.5 keV. By using X-ray spectrometry following irradiation, sensitive Cu analysis can be accomplished. Because of the short range of the low-energy X rays, near-surface analytical data are obtained without chemical etching. A combination of neutron activation with X-ray spectrometry also can be applied to other elements, such as Zn and Ge. 

Semi quantitive speetrographie analysis of other elements 2ppm... 

Ultimate analysis-an analysis to determine the amounts of basic feed constituents. These constituents are moisture, oxygen, carbon, hydro- gen, sulfur, nitrogen, and ash. In addition, it is typical to determine chloride and other elements that may contribute to air emissions or ash- disposal problems. Once the ultimate analysis has been completed, Dulong s formula can be used to estimate the heating value of the sludge, Dulong s formula is ... 

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