Isotopic analyses definition

Whether this is true or not, meteorites give us one definite piece of information. Isotopic analysis shows that each element in a meteorite has the same isotopes in the same percentages that this same element has on earth. The accepted explanation for this fact is that meteorites and the earth share a common origin and that they became separated after the elements were created. 

Pathway of reaction, 1167 consecutive reactions, 1259 definition, 1259 and FTTR spectroscopy, 1259 hydrogen evolution reaction, 1259 isotopic analysis. 1259 mechanism, 1259 parallel reactions, 1259 Permitivity of free space. 875 Perez, 1519... 

Measurement of fecal zinc does not yield the value 0, but rather the total zinc excreted (of dietary and endogenous origin). Thus, determination of total zinc in the diet and the fecal pool will not provide an estimate of the absorption of zinc. However, if the isotopic makeup of the dietary zinc is suitably altered, via administration of a labeled diet, then isotopic analysis of the diet and of the corresponding fecal pool will satisfy the requirements of the above definition. For the simplest case where the natural isotopic composition of a single component of the diet has been altered (single-labeling) an estimate of the fractional absorption (F] ) of the mineral from the labeled diet component, can be made from two simultaneous equations, as follows (See Table I for definitions) ... 

Both 6 0 and 6 C values for each end-member cement generation plot within narrow zones (Fig. 15), allowing a precise definition of the conditions under which the individual cement generations formed, albeit based on a small data set. The data show that the quantitative approach to isotope analysis provides added p cision to routine bulk-rock isotope interpretation methods in the study area. The technique used in this study may be applicable to other geological provinces, provided different cement generations do not have the same chemical composition. The image analysis technique is particularly valuable for rocks in which pure or nearly pure samples of carbonate cement end-members do not exist. 

This kind of model has not been applied in any detail to Mars. A problem that confronts it on that planet is the observation that Xe on Mars and Earth, while displaying comparable light-isotope ratios, is compositionally different at the heaviest isotopes in ways that cannot be explained by variable additions of or fission Xe to either or both atmospheres. As discussed below, it appears that Xe compositions on the two planets reflect mass fractionation of two isotopically distinct primordial starting compositions, in conflict with the hypothesis of a common planetesimal source. Venus is the key. Even a moderately accurate isotopic analysis of Venusian Xe, where no data presently exist and where the nonradiogenic Xe compositions predicted by the two models—Earth-like if supplied by porous planetesimals, and solar-like if unfractionated by hydrodynamic escape—are very different, should rule definitively between them—or create problems for both. 

Appropriate sample digestion, element-matrix separation techniques, aerosol desolvation [67, 68], and use of an alternative sample introduction system [66, 69, 70] are means to avoid (some cases of) spectral overlap. In present-day ICP-MS instrumentation, some more general strategies to tackle spectral overlap can also be deployed. In general, spectral interferences are an even greater nuisance in isotopic than in trace element analysis. A first reason for this lies in the fact that in isotopic analysis, at least two nuclides should display a signal free from spectral overlap. Moreover, whereas a limited extent of spectral overlap (e.g., 0.1-1%) may be negligible in trace element determination, this is definitely not the case in isotope ratio determination. 

The isotopic distribution of lead (IDMS) in shed teeth from children has been shown to be useful in studies of the history of exposure to lead, including the definition of the source of the exposure, e.g., mine dust vs. food (Gulson and Wilson 1994), so IDMS certainly has important applicability, if not for routine determinations. ICP/MS, however, is easier, more sensitive, allows for multi-element analysis, and provides isotopic data. 

Isotope dilution analysis is the definitive method for the quantitative analysis of many compounds but is usually only carried out in specialist laboratories. 

The observation of hidden reactions during solvolysis, through the use of chiral or isotopically labeled substrates has created considerable excitement in communities interested in the mechanisms of nonenzymatic and enzyme catalyzed reactions. These hidden reactions reveal something interesting about reaction mechanisms. However, chemists and biochemists are still working on the problem of extracting simple and definitive conclusions from analysis of data for these isomerization reactions. 

A reliable authenticity assessment is concluded from the simultaneous consideration of multielement IRMS and enantioselective analysis. The differences of the stable isotope ratios of linalool and linalyl acetate are depicted as a three-dimensional plot of A values (d values of linalool minus d values of linalyl acetate for oxygen, hydrogen and carbon) (Fig. 17.15). This plot shows that the commercial samples S1-S5 are different from all the other samples investigated. Linalool and linalyl acetate of S1-S5 definitely are not genuine lavender oil compounds. 

The availability of stable isotope-labeled PA makes an accurate quantitative determination of this imino acid possible. A short high-performance liquid chromatography (HPLC) run prior to the mass spectrometer inlet will result in a discrete peak of PA. For the definitive diagnosis of AASA dehydrogenase deficiency, a simultaneous determination of AASA would be preferred. The absence of a commercially available labeled standard leaves this analysis in the experimental stage. 

Deep state experiments measure carrier capture or emission rates, processes that are not sensitive to the microscopic structure (such as chemical composition, symmetry, or spin) of the defect. Therefore, the various techniques for analysis of deep states can at best only show a correlation with a particular impurity when used in conjunction with doping experiments. A definitive, unambiguous assignment is impossible without the aid of other experiments, such as high-resolution absorption or luminescence spectroscopy, or electron paramagnetic resonance (EPR). Unfortunately, these techniques are usually inapplicable to most deep levels. However, when absorption or luminescence lines are detectable and sharp, the symmetry of a defect can be deduced from Zeeman or stress experiments (see, for example, Ozeki et al. 1979b). In certain cases the energy of a transition is sensitive to the isotopic mass of an impurity, and use of isotopically enriched dopants can yield a positive chemical identification of a level. 

An outstanding feature of inorganic mass spectrometry is its determination of precise and accurate isotopic abundances and isotope ratios. Isotopes of the same element (of the same number of protons or atomic number of element, Z) are, by definition, nuclides with different mass m and mass number A (A = Z + N) due to the different number of neutrons (N) in the nucleus. Isotope analyses are of special interest for characterizing the composition of samples with respect to stable and unstable isotopes in quite different concentration ranges - from the analysis of matrix elements down to the trace and ultratrace concentration level.1-9 Of 1700 isotopes, nearly 16 % (264 isotopes) are stable. The chemical elements Tc, Pm, Th, U and the transuranic elements do not possess stable isotopes. 

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