Nitrogen isotope analysis

A smaller number of individuals, 132 samples, was analyzed for stable isotopes of nitrogen. There were two objectives to the nitrogen isotope analysis 1) to determine the amount of animal protein in the diet and to look for variation between the sexes and 2) to determine when infants were weaned from the breast. These objectives were addressed by selecting at least ten individuals, when available, from a number of age classes. Figure 1.1 illustrates the age distribution of the sample. Table 1.3 shows the results of these analyses. Individual 5 N values are provided in Herring et al. (1998). 

Ambrose, S.H. 1986 Stable carbon and nitrogen isotope analysis of human and animal diet in Mrica. Journal of Human Evolution 15 707-731. 

Atwell L, Hobson KA, Welch HE. 1998. Biomagnilication and bioaccumulation of mercury in an arctic marine food web insights from stable nitrogen isotope analysis. Can J Fish Aquat Sci 55 1114-1121. 

Macko, S. A., Uhle, M. E., Engel, M. H. and Andrusevich, V. (1997) Stable nitrogen isotope analysis of amino acid enantiomers by gas chromatography combustion/isotope ratio mass spectrometry. Analytical Chemistry 69, 926 929. 

Merritt, D. A. and Hayes, J. M. (1994) Nitrogen isotopic analysis by isotope ratio monitoring gas chromatography mass spectrometry. Journal ofthe American Society ofMass Spectrometry 5,387 397. 

Styring, A. K., Sealy, J. C. and Evershed, R. P. (in press) Resolving the bulk 81SN values of ancient human and animal bone collagen via compound specific nitrogen isotope analysis of constituent amino acids. Geochimica et Cosmochimica Acta. 

MS is the method used in stable isotope analysis. By enriching samples with a particular isotope, that sample or isotope can be followed as it passes through the environment. This technique has been particularly useful in studying the fate of nitrogen as 15N in environmental studies. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

In recent years, tremendous progress has been achieved in the analysis of the isotope composition of important trace compounds in the atmosphere. The major elements - nitrogen, oxygen, carbon - continually break apart and recombine in a multitude of photochemical reactions, which have the potential to produce isotope fractionations (Kaye 1987). Isotope analysis is increasingly employed in studies of the cycles of atmospheric trace gases e.g., CH4 and N2O, which can give insights into sources and sinks and transport processes of these compounds. The rationale is that various sources have characteristic isotope ratios and that sink processes are accompanied by isotope fractionation. 

Grady MM, PiUinger CT (1990) ALH 85085 nitrogen isotope analysis of a highly unusual primitive chondrite. Earth Planet Sci Lett 97 29 0... 

Sweeney RE, Kaplan IR (1980) Natural abundance of as a source indicator for near-shore marine sedimentary and dissolved nitrogen. Mar Chem 9 81-94 Sweeney RE, Liu KK, Kaplan IR (1978) Oceanic nitrogen isotopes and their use in determining the source of sedimentary nitrogen. In Robinson BW (ed.) DSIR Bull 220 9-26 Swihart GH (1996) Instrumental techniques for boron isotope analysis. Rev Miner 33 845-862 Swihart GH, Moore PB (1989) A reconnaissance of the boron isotopic composition of tourmaline. Geochim Cosmochim Acta 53 911-916... 

In 1953, Billings et al. (17) studied the water vapor reaction with a lssHg source. The experiments were carried out in a flow system with nitrogen as carrier gas. The mercury oxide formed was found to be enriched in mHg, relative to its natural abundance. Similarly, with a -"-Hg lam)), an enriclnnent in 2,2Hg was observed (18). The isotopic analysis of mercury product in these studies was made by interferometry. 

Tittlemier SA, Fisk AT, Hobson KA, Norstrom RJ (2002) Examination of the Bioaccumulation of Halogenated Dimethyl Bipyrroles in an Arctic Marine Food Web Using Stable Nitrogen Isotope Analysis. Environ Pollut 116 85... 

Grady, M. M. Pillinger, C. T. 1990 ALH 85085 nitrogen isotopic analysis of a highly unusual primitive chondrite. EPSL 97, 29—40. 

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