Compound specific isotope ratios

Zou, L., X. Wang., Callahan, J., Culp, R.A., Chen, R.F., Altabet, M., and Sun, M. (2004) Bacterial roles in the formation of high-molecular-weight dissolved organic matter in estuarine and coastal waters evidence from lipids and the compound-specific isotopic ratios. Limnol. Oceanogr. 49, 297-302. 

GC-C-IRMS The combination of a gas chromatograph with a combustion cell and an isotope ratio mass spectrometer allows the determination of compound-specific isotope ratios, which for some compound classes such as the nucleobases is the only method to determine whether they are indigenous to the meteorite or terrestrial contamination (J). 

Keywords values, (S N values, Corg/Ntotal ratios, compound-specific isotope ratios, lignin phenols,... 

Since the P T procedure includes various phase transition steps that may shift the isotopic signature of the analytes (evaporation, sorption and condensation), the P T method parameters of purge time, desorption time and injection temperature have been carefully evaluated for the determination of the 8 C-values. The compound specific isotope ratios of 10 different VOCs ranging from the unpolar benzene to the polar MTBE as listed in Table 4.6 were determined (Zwank, 2003 Zwank and Berg, 2013). 

Compound specific isotope ratio monitoring The isotope composition of individual components constituting a complex mixture can be determined by... 

Figure 15 Compound specific isotope ratio monitoring interface. For clarity, the devices for backflushing the solvent, for effluent diversion from the ion source, and for reference gas injection are not shown.

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. 

G. Gleixner, H.-L. Schmidt (1998) On-line determination of group-specific isotope ratios in model compounds and aquatic humic substances by coupling pyrolysis to GC-C-IRMS. ACS Symbosium Series 707 34-46... 

With respect to the different shifts of S13C-values in the recovery procedure it has to be noted, that a satisfactory determination of carbon isotope ratios depends not only on the analytical methods applied but also on the individual substances analysed. Therefore, in order to evaluate the quality of compound specific isotope analyses of riverine contaminants measurements of field samples have to be accompanied by recovery experiments of individual substances. 

Compound-specific isotope analysis Determination of the isotopic ratio of the carbon, nitrogen, hydrogen, sulfur, or oxygen contents of a single compound. The isolation of the single compound is usually achieved by some form of either off-line or on-line preparation in which gas chromatography is an important step. 

The development of GC coupled via a combustion furnace to an IRMS (GC-C-IRMS) has allowed the analysis of individual compounds occurring at trace levels in very complex mixtures. Sometimes referred to as compound specific isotope analysis or isotope ratio monitoring MS (GC-irmMS), this technique has opened new fields of research in areas such as organic geochemistry, food science, medicine, nutrition, sport, forensic science, archaeology, soil science, and extraterrestrial science. The chromatographic separation in connection with the combustion of the analyte, however, exerts the strongest influence on the uncertainty of the measurement. Multidimensional GC (GC/GC) has also been coupled to IRMS for the authentication of flavor components. 

Stable isotope ratio mass spectrometers that interface directly to a gas chromatograph are commercially available. This type of analysis is known variously as gas chromatography-isotope ratio mass spectrometry (GC-IRMS), gas chromatography-combustion isotope ratio mass spectrometry, or compound-specific isotope analysis. The same principle of operation has also been used for more general isotope ratio analyses, where the components of interest are combusted as bulk samples. This type of arrangement, known as continuous flow-isotope ratio mass spectrometry, allows rapid automated analyses of and... 

The compound specific isotope analysis (CSIA) has been successfully used in the assessment of in situ remediation of contaminated environments, identification of pollutant degradation pathways, or the verification of contaminant sources. In these types of studies, the sensitivity of isotope ratio monitoring GC-MS (irm-GC-MS) is often a limiting factor, since concentrations of organic contaminants in groundwater are very often in the low pg/L range. Hence, in order to be able to routinely use irm-GC-MS techniques in environmental studies, efficient extraction procedures are required. 

Compound specific isotope analysis, the isotope ratio MS analysis of individual compounds after chromatographic separation followed by the online conversion to simple gases, contrary to a -> BSIA. 

Haas, K., Feldmann, J., Wennrich, R., and Stark, K. J. (2001) Species-specific isotope-ratio measurements of volatile tin and antimony compounds using capillary GC-ICP-time-of-flight-MS. Fresenius J. Anal. Chem., 370, 587-96. 

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