Compound-specific isotopic analysis

GC-C-IRMS instrumentation enables the compound-specific isotope analysis of individual organic compounds, for example, n-alkanes, fatty acids, sterols and amino acids, extracted and purified from bulk organic materials. The principle caveat of compound-specific work is the requirement for chemical modification, or derivatisation, of compounds containing polar functional groups primarily to enhance their volatility prior to introduction to the GC-C-IRMS instrument. Figure 14.7 summarises the most commonly employed procedures for derivatisation of polar, nonvolatile compounds for compound-specific stable isotope analysis using GC-C-IRMS. 

Bowen, G. J. and Revenaugh, J. (2003) Interpolating the isotopic composition of modern meteoric precipitation. Water Resources Research 39(10), 1299 Brand, W. A., Tegtmeyer, A. R. and Hilkert, A. (1994) Compound specific isotope analysis extending toward 15N/14N and 180/160. Organic Geochemistry 21, 585 594. 

Finally, Chapters 14 16 deal with innovative applications in this field such as mass spectrometric compound-specific isotopic analysis, secondary ion mass spectrometry... 

Compound-specific isotope analysis (CSIA) by GC-IRMS became possible in 1978 due to work of Mathews and Hayes [634], based on earlier low-precision work of Sano et al. [635]. The key innovation was the development of a catalytic combustion furnace based on Pt with CuO as oxygen source, placed between the GC exit and the mass spectrometer. The high pressure of helium (99.999% purity or better) ensures that all gas flows are viscous. After being dried in special traps avoiding formation of HC02 (i. e., interferes with 13C02) by ion-molecule reactions in the ion source, the C02 is transmitted to a device that regulates pressure and flow and then into the ion source [604]. 

Newer instrumental methods of potential utility in organic analysis of environmental and geological biomarkers are compound specific isotope analysis (CSIA) and carbon-14 dating with accelerator mass spectrometry (AMS). CSIA provides the carbon isotope composition of individual... 

Lichtfouse, E. (2000). Compound-specific isotope analysis, application to archael-ogy, biomedical sciences, biosynthesis, environment, extraterrestrial chemistry, food science, forensic science, humic substances, microbiology, organic geochemistry, soil science and sport. Rapid Commun. Mass Spectrom. 14, 1337-1344. 

Canuel et al., 1997). This recurring theme of overlapping sterol markers in different organic matter sources indicates that caution should be advised when using sterols solely to distinguish between land and aquatic sources (Volkman, 1986 Jaffe et al., 2001). Instead, biomarker source identifications should be corroborated across lipid compound classes and using bulk and compound-specific isotope analysis. 

Figure 9.50a Compound-specific isotope analysis (CSIA) of suspended particulate organic matter (SPOM), lipids, and plant pigments in several estuaries on the Texas coast (USA). The range of 513C in these estuaries was —18 %o to —22 %o. (Modified from Qian et al., 1996.)...

Sources of PAHs can be distinguished by using select ratios. For example, ratios of total methylphenanthrenes to phenanthrene is used to identify PAHs as pyrolytic or petrogenic sources. Other work has resorted to the application of compound-specific isotope analysis (CSIA), to constrain better anthropogenic sources of PAHs. 

Qian, Y., Kennicutt, M.C., Svalberg, J., Macko, S.A., Bidigare, R.R., and Walker, J. (1996) Suspended particulate organic matter (SPOM) in Gulf of Mexico estuaries compound-specific isotope analysis and plant pigment compositions. Org. Geochem. 24, 875-888. 

Dempster HS, Sherwood-Lollar B, Feenstra S (1997) Tracing organic contaminants in groundwater a new methodology using compound-specific isotopic analysis. Environ SciTechnol 31 3193-3197... 

Sephton M. A. and Gilmour I. (2001b) Compound specific isotope analysis of the organic constituents in carbonaceous chondrites. Mass Spec. Rev. 20, 111-120. 

Hayes J. M., Freeman K. H., Popp B. N., and Hoham C. H. (1990) Compound-specific isotope analysis a novel tool for reconstruction of ancient biogeochemical processes. In Advances in Organic Geochemistry 1989 (eds. B. Durand and F. Behar). Pergamon, Oxford, pp. 1115-1128. 

Additionally, 19 Lippe water samples collected in 1999 were investigated by compound specific isotope analysis. Also a sufficient detection of numerous anthropogenic contaminants was achieved in terms of adequate concentration levels and effectual gas chromatographic separation as illustrated in Fig. 6. 

Yanik PJ, O Donnell TH, Macko SA (2003a) Source apportionment of polychlorinated biphenyls using compound specific isotope analysis. Org Geochem 34, 239-251. 

CSIA compound specific isotope analysis water solubility... 

The aim of this review is to provide a critical evaluation of recently published analytical methods available for (i) the quantification of fuel oxygenates in environmental aqueous samples and (ii) the characterization of the environmental fate of MTBE in groundwater with the use of compound-specific isotope analysis (CSIA). For a detailed evaluation of methods available for air, water and soil analysis of dialkyl ethers and alcohols and their specific advantages and drawbacks, the reader is also referred to previous reviews. [3-6]. 

Compound-specific isotope analysis (CSIA) is a rather new tool in environmental analysis. It is not used for quantitative analysis of organic compoimds but rather for the characterization of environmental fate by monitoring changes in the isotopic composition of organic molecules. Analytical aspects are covered here because this rather new area of research is expected to mature to a standard tool in environmental analysis that will complement the quantitative analysis in the environment [70]. 

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