Carbon isotope tracers

Shen CD, Sun YM, Yi WX, Peng SL, Li ZA (2001) Carbon isotope tracers for the restoration of degenerated forest ecosystem. Quaternary Sciences 21 452 160 (in Chinese with English abstract)... 

Adsorbents, extraction procedures, organic pollutants, 113 Aerosol, problems in measuring, coal combustion, 312-317 Aerosol carbon data, results and discussion, carbon isotope tracers, 270-275... 

Quade J., Chivas A. R., and McCulloch M. T. (1995) Strontium and carbon isotope tracers and the origins of soil carbonate in South Australia and Victoria. In Arid-Zone Paleoenviron-ments, Palaeogeogr, Palaeoclimatol. Palaeoecol. 113 (ed. A. R. Chivas), pp. 103-117. 

A series of tracer techniques have been developed for calculation of the source contribution to EC concentrations, including use of potassium (K) as a woodsmoke tracer (Currie et al., 1994) and use of the carbon isotopic tracers C and C (Klouda et al., 1988 Lewis et al., 1988 Currie et al., 1989). By this procedure 47% of the EC in Detroit, 93% in Los Angeles, and 30 to 60% in a rural area in Pennsylvania have been attributed to motor vehicle sources (Wolff and Korsog, 1985 Pratsinis et al., 1988 Keeler et al., 1990). The corresponding contribution of diesel emissions to EC concentrations in Western Europe is estimated to be 70 to 90% (Hamilton and Mansfield, 1991). EC was also a major constituent of the Kuwait oil fires, with concentrations as high as 178 mg m inside the plume (Cofer et al., 1992 Daum et al., 1993 and references therein). 

Although many overall rearrangements can be formulated as a series of 1,2-shifts, both isotopic tracer studies and con utational work have demonstrated foe involvement of other species. These are bridged ions in which hydride or alkyl groups are partially bound to two other carbons. Such structures can be transition states for hydride and alkyl-group shifts, but some evidence indicates that these structures can also be intermediates. 

The amounts of the standard isotopic species and the tracer isotopic species are represented by X and X for the sample and the reference material. The reference substance is chosen arbitrarily, but is a substance that is homogeneous, available in reasonably large amounts, and measurable using standard analytical techniques for measuring isotopes (generally mass spectrometry). For instance, a sample of ocean water known as Standard Mean Ocean Water (SMOW) is used as a reference for and 0. Calcium carbonate from the Peedee sedimentary formation in North Carolina, USA (PDB) is used for C. More information about using carbon isotopes is presented in Chapter 11. 

Some aspects of the biochemistry of metabolic processes affecting nutrients appear to have significant consequences for the expected behavior of stable carbon isotopes as tracers of diet. Specifically, we have seen that the simple model of a total scrambling of carbon atoms during endogenous biosynthesis is inconsistent with the expected pathways of some nutrients, whereas other isotopic records in ancient human tissues can be adequately accounted for by this model. 

Boutton, T.W. 1991 Tracer studies with C-enriched substrates humans and large animals. In Coleman, D.W. and Fry, B., eds.. Carbon Isotope Techniques. Academic Press, San Diego 219-242. 

The characteristics of nuclei described here are intimately related to how certain species figure prominently in chemistry (such as dating materials by determining their carbon-14 content). The use of isotopic tracers is a technique that finds applications in all areas of chemistry. 

Fluid and gas samples were also collected for hydrocarbon and nonhydrocarbon gas compositional analyses (GC), carbon isotopes of C02 (GCIRMS), and for tracer analyses (GC-MS). 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of substrate oxidation, carbon dioxide formation (including C02 breath tests), glucose oxidation, and fat oxidation in normal and diseased states. Quantification of the rate and extent of substrate oxidation can be achieved by using a specific or C-substrate which upon oxidation releases radioactive carbon dioxide. 

Work on the biosynthesis of cholesterol began in earnest after Rudolf Schoenheimer and David Rittenberg, at Columbia University, developed isotopic tracer techniques for the analysis of biochemical pathways. In 1941, Rittenberg and Konrad Bloch were able to show that deuterium-labeled acetate (C2H, COO ) was a precursor of cholesterol in rats and mice. In 1949, James Bonner and Barbarin Arreguin postulated that three acetates could combine to form a single five-carbon unit called isoprene. 

Early isotope tracer experiments by David Shemin permitted the elucidation of the formation of the immediate precursor of the porphyrin needed for the cytochromes and for hemoglobin. These studies indicated that the glycine methylene carbon and nitrogen were incorporated along with both carbons of acetate. Subsequent enzymatic studies in both bacteria and animals revealed a condensation reaction between succinyl-CoA and glycine to yield 5-amino-levulinate and C02 (presumably by way of an enzyme-bound /3-keto acid, a-amino-/3-ketoadipate) (fig. 22.13). 

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