Isotope fingerprinting

The actual ratio of 13C to 12C is determined using an isotope-ratio-mass spectrometer. The actual ratio is then compared with a standard using the following equation to calculate the ratio difference in parts per thousand  

FIGU RE 4.16 Relative solubilities of BTEX, MTBE, and the lead scavengers EDC and EDB. 

The most widely used standard is a belemnite from the Peedee Formation in South Carolina (PDB) therefore, some ratios may be expressed as negative values. Most carbon isotope ratio correlations are made on the C15+ fraction of crude oil because it is less affected by degradation processes. Valid correlations using carbon isotopes can only be conducted on the same fractions of samples. 

FIGURE 4.17 Additional aromatic compounds, sulfur, and sterene distribution based on gas chromatograph results for two LNAPL samples from adjacent sites. 

FIGURE 4.18 Two-component plot of 13C/12C isotope ratio from the saturated and aromatic 

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Vogel, J.C., Eglinton, B. and Auret, J.M. 1990 Isotopic fingerprints in elephant bone and ivory. Nature 346 747-749. 

Almost complete elemental coverage (isotopic fingerprinting)... 

Example Ruthenium exhibits a wide isotopic distribution where the ° Ru isotope can be used as a marker during assignment of mass differences. Moreover, the strong isotopic fingerprint of Ru makes it easily detectable from mass spectra and even compensates for a lack of information resulting from moderate mass accuracy (Fig. 3.10). 

Richer P, Bottinga Y, Javoy M (1977) A review of H, C, N, O, S, and Q stable isotope fractionation among gaseous molecules. Ann Rev Earth Planet Sci 5 65-110 Richter FM (2007) Isotopic fingerprints of mass transport processes. Geochim Cosmochim Acta 71 A839... 

Guiet et al. (2003) demonstrated that deuterium (2H) distribution in fatty acids was non-statistical and could be related to isotopic discrimination during chain extension and desaturation. Petroselinic acid (C18 1A6) (Fig. 21.4), a fatty acid characteristic of the seeds of the Apiaceae, has been shown to be biosynthesized from palmitoyl-ACP (C16 0) by two steps, catalysed by a dedicated A4-desaturase and an elongase. The isotopic profile resulting from this pathway is similar to the classical plant fatty acid pathway, but the isotopic fingerprint from both the desaturase and elongase steps shows important differences relative to oleic and linoleic acid biosynthesis. 

A better representation of the three-dimensional lead isotope fingerprint can be made by using a multivariate discriminant analysis. Figure 3 shows the characteristic lead isotope composition of the same three ore deposits that was prepared by using multivariate discriminant analysis (Pollard, M., University of Cardiff, personal communication in 1986). It shows clearly, as the two-dimensional diagrams do not, that these fields may be resolved by using all three isotopic ratios. 

These associations are, at present, only tentative and assume a roughly single-stage lead isotope evolution, with negligible contamination of the copper ore deposits by lead derived from older country rocks. Nevertheless, this approach should be used as a basis for further field exploration of the areas in question. The mines and ore deposits in north and northwestern Turkey have recently been explored by a team from the Max Planck Institute for Nuclear Physics in Heidelberg (42, 59), and we hope that there will soon be more information available for the lead isotope fingerprints of Anatolian ore sources. Information available so far proves only that Troy did not get copper from its hinterland and does not identify its source. 

In the cases, increases in neodymium-isotope ratios along water advection pathways are attributed to local volcanic sources. Thus, it is likely that addition of neodymium from volcanic particles imparts the distinctive neodymium-isotopic fingerprint to Pacific seawater, which is ultimately intermediate to values of recent volcanic and old continental sources. 

Recently, deuterium-induced isotope effects on Li chemical shifts in organolithium compounds have been observed [51] and based on this observation, the isotopic fingerprint method was developed as a tool for structural investigations in the field of organolithium compounds. With this method, typical Li multiplets, which are characteristic of the aggregation state. 

The isotopic fingerprint method has been applied to study the aggregation of alkyl and aryl lithium compounds [51,52,72,73], of lithium disopropylamide [72] and of mixed aggregates between methyllithium and Lil [51] as well as LiBr [53]. These studies revealed also the existence of isotope shifts transmitted over more than two bonds. In all cases high-frequency shifts for the Li resonance were observed. 

Figure 5 Deuterium-induced isotopic fingerprints in Li NMR spectra of partially deuteriated organolithium aggregates (a) phenyllithium monomer (THF/penta-methyldiethylenetriamine — 122°Q (b) phenyllithium dimer (Et20/tetramethylethyl-enediamine -111°C) (c) methylhthium tetramer (R=CHj EtjO, — 92 Q (d) fluxional phenyllithium tetramer (Et20, — 102 C). The measu H/ H isotope shifts for 5( Li) are 19.2, 10.4, 15.6, and 7.0 ppb, respectively. All systems were Li labelled and 50% of the organic ligands were perdeuterated v C Li) = 58.88 MHz...

In contrast, stable isotopic study offers more powerful insight from the geological record. Biochemical processes leave isotopic fingerprints to calibrate the evolutionary history of metabolic processes inferred from molecular work. Conventional stable isotope study has been used to infer the global role of major processes such as photosynthesis (Schidlowski Aharon 1992) but... 

Studies carried out in Antarctic snow and ice (52, 53) on the isotopic composition of Pb have proved unequivocally that recent snow layers, and hence the present Antarctic troposphere are contaminated by anthropogenic Pb. Isotopic fingerprinting also proved two different sources a natural component associated with aeolian dust and an anthropogenic component. The possible origin of this Pb-rich aerosol is hypothesised to be South America. 

An added piece of information is available in the isotopic fingerprints in a mass spectrum. The isotopic ratios can assist in Identifying the species and fragmentation patterns of the substance being analyzed. The ability of SIMS to detect different Isotopes of an element adds richness to the data obtained and flexibility to the analysis. 

Eerkens, Jelmer W., Gregory S. Herbert, Jeffrey S. Rosenthal, and Howard J. Spero. 2005. Provenance analysis of Olivella biplicata shell beads from the California and Oregon Coast by stable isotope fingerprinting. Journal of Archaeological Science 32 1501-1514. 

Sulfur isotope fractionation is important in the study of atmospheric gases, sulfur in the oceans (Section 5.4.4.1) and in living organisms. Microbes use 32S in preference to 34S during microbial sulfate reduction providing a sulfur isotope fingerprint for a... 

The isotopic fingerprinting of photosynthesis. Photosynthesis is currently an important means of fixing inorganic carbon and is used by plants, algae, bacteria, and Archaea. A particularly important enzyme (catalyst) in this process is Rubisco, the official shortened name for a molecule with a much more intricate systematic name. The reactions which take place in this process operate according to the Calvin-Benson Cycle and lead to isotopic fractionations of up to 30%o. 

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