Review on Pre-enrichment Methods in Compound Specific Carbon Isotope Analysis of Chlorinated Hydrocarbon in Water

Highly accurate determination of Compound Specific Carbon Isotope Analysis (CSIA) of chlorinated hydrocarbons is of great significance in tracing the source and revealing the biodegradating progress of pollutants. The isotopic composition of organic contaminations may be stable or varied in the process of environmental transformation. We can trace the source of contaminations if the composition is stable and can evaluate the probability and degree of degradation of contaminations. This paper summarizes solid-phase microextraction, static headspace analysis, purge and trap method and compound specific isotope analyses of chlorinated hydrocarbon in water, using combinations of these pretreatment methods, Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS), and compares the three methods. Compared with liquid-liquid extraction, solid-phase micro extraction, static headspace analysis, purge and trap method are all solvent-free enrichment techniques, producing no secondary pollution, less interference, and the resolution and accuracy of the analysis of GC-C-IRMS is improved. No, or little, isotopic mass fractionation occurred during the isotope analysis of chlorinated hydrocarbon in water by combining these solvent-free enrichment techniques with GC-C-IRMS, of which the precision of the analysis is less than 1‰. The detection limit decreased along with the methods of static headspace analysis, solid-phase micro extraction, purge and trap method. Purge and trap is the most popular method because of its good reproducibility and low detection limit for the compound specific isotope analysis of chlorinated hydrocarbon in Water. The combinations of in-needle microextraction, in-tube microextraction, stir bar sorptive extraction or headspace sorptive extraction with GC-C-IRMS have a bright future.