Stable isotopes isotopic fractionation

In nature, oxygen occurs in three stable isotopic species oxygen-16 [14797-70-7] O, 99.76% oxygen-17 [13968-48-4], 0.038% and oxygen-18 [14797-71-8], 0.20% (7). Commercial fractional distillation of water produces concentrations of as high as 99.98% concentrations up to 55% are also produced. The isotope has been used to trace mechanisms of organic reactions. 

Irreversible processes are mainly appHed for the separation of heavy stable isotopes, where the separation factors of the more reversible methods, eg, distillation, absorption, or chemical exchange, are so low that the diffusion separation methods become economically more attractive. Although appHcation of these processes is presented in terms of isotope separation, the results are equally vaUd for the description of separation processes for any ideal mixture of very similar constituents such as close-cut petroleum fractions, members of a homologous series of organic compounds, isomeric chemical compounds, or biological materials. 

Stable isotope analyses of the organic fraction of bone and of food samples was carried out on a Micromass Prism Mass Spectrometer in the Stable Isotope Laboratory, Department of Physics, University of Calgary, under the direction of H.R. Krouse. Collagen samples were combusted in a Carlo Erba gas analyser which provides information on the carbon and nitrogen content of the samples andintroduces Nior CO gases into the mass spectrometer for analysis of nitrogen or carbon stable isotopes, respectively. 

Stable Isotope Analysis, Bone Organic Fraction... 

Krueger, H.W. and Sullivan, C.H. 1984 Models for carbon isotope fractionation between diet and bone. In Tumland, J.R. and Johnson, P.E., eds.. Stable Isotopes in Nutrition. Washington D.C, American Chemical Society Symposium Series, No. 258 205-220. 

Macko, S.A., Estep, M.L.E., Engel, M.H. and Hare, RE. 1986 Kinetic fractionation of stable nitrogen isotopes during amino acid transamination. Geochimica et Cosmochimica Acta 50 2143-2146. 

Hohson, K.A. and Clark, R.G. 1992 Assessing avian diets using stable isotopes 11 factors influencing diet-tissue fractionation. The Condor 94 181-188. 

There are approximately 200 other proteins present in bone, though most of them are present only in trace amounts (Delmas et al., 1984 Linde et al., 1980, as cited in van Klinken, 1991). The second most common bone protein, osteocalcin, comprises 1-2 weight % of total fresh bone. Osteocalcin bonds with both the bone mineral fraction and bone collagen, but it seems to be unstable in solutions. Due to its small molecular size and strong mineral stabilization, osteocalcin can survive up to 50.000 years (C.l. Smith et al., 2005), and it may offer an alternative to the use of collagen in paleoenvironmental stable isotope research. However, osteocalcin s role and importance in this field of study has yet to be defined (Collins et al., 2002). 

Tieszen, L.L., Boutton, T.W., Tesdahl, K.G., Slade, N. A. (1983). Fractionation and turnover of stable carbon isotopes in animal tissues implications for dl3C analysis of diet. Oecologia, Vol. 57, pp. 32-37. 

Farquhar, G.D., Hubick, K.T., Condon, A.G. Richards, R.A. (1988). Carbon isotope fractionation and plant water-use efficiency. In Applications of Stable Isotope Ratios to Ecological Research, ed. P.W. Rundel, J.R. Ehleringer K.A. Nagy, pp.21 0. New York Springer-Verlag. 

Each different unstable isotope has its own characteristic rate of decomposition. Some isotopes survive for only a fraction of a second, but others decompose slowly, sometimes over thousands of years. Most of chemistry involves the stable isotopes, so we defer further consideration of nuclear decomposition until Chapter 22, which covers nuclear processes In detail. 

Elements such as C, N, O, S, and Cl that are components of many organic compounds exist naturally as mixtures of stable isotopes. The ratios of these in a compound reflect the different rates of reaction at isotopically labeled positions, and therefore reflect the fractionation—biotic or abiotic—by which it was synthesized or to which the compound has been subjected. Techniques have been developed whereby the ratios C/ C (5 C), (5 N), (5 0),... 

Drenzer NJ, T1 Eglinton, CO Wirsen, HD May, Q Wu, KR Sowers, CM Reddy (2001) The absence and application of stable carbon isotope fractionation during the reductive dechlorination of polychlorinated biphenyls. Environ Sci Technol 35 3310-3313. 

Morasch B, HH Richnow, A Vieth, B Schink, RU Meckenstock (2004) Stable isotope fractionation caused by glycyl radical enzymes during bacterial degradation of aromatic compounds. Appl Environ Microbiol 70 2935-2940. 

Morasch B, HH Richnow, B Schink, A Vieth, RU Mweckenstock (2002) Carbon and hydrogen stable isotope fractionation during aerobic bacterial degradation of aromatic hydrocarbons. Appl Environ Microbiol 68 5191-5194. 

Nijenhuis 1,1 Andert, K Beck, M Kastner, G Diekert, H-H Richow (2005) Stable isotope fractionation of tetrachloroethene during reductive dechlorination by Sulfospirillum multivorans and Desulfitobac-terium sp. strain PCE-S and abiotic reactions with cyanocobalamin. Appl Environ Microbiol 71 3413-3419. 

---