Analysis of Compound-Specific Chlorine Stable Isotopes of Vinyl Chloride by Continuous Flow–Isotope Ratio Mass Spectrometry (FC–IRMS)

A new method for determining compound-specific chlorine stable isotope was developed for vinyl chloride (VC). The analysis is carried out on a continuous flow–isotope ratio mass spectrometer (CF–IRMS) with special collectors for m/z 64 and 62. The precision of this technique is better than ± 0.16‰ (1σ) for pure phase gas injection and headspace solid phase microextraction (SPME) injection. The new methodology was tested in a confined sandy aquifer contaminated with VC located near the city of Ferrara, northern Italy. The VC isotopic signatures (37Cl and 13C) showed that the VC is not a primary manufactured compound and is a byproduct of production of petrochemicals in the Ferrara region during the 1970s and 1980s. The isotope data also suggested VC is attenuated by biodegradation along the groundwater flow system. The development of compound-specific isotope analysis (CSIA) for VC offers a new tool for fingerprinting sources and processes that affect VC in groundwater.