Determining Chlorine Isotope Composition in Environmental Organic Pollutants by GC/MS

Anat Bernstein, Ben-Gurion University, Sde Boker Campus, Israel
Almog Gafni, Ben-gurion University, Sde Boker Campus, Israel
Faina Gelman, Geological Survey Of Israel, Jerusalem, Israel

Compound Specific Isotope Analysis (CSIA) enables to study degradation processes of organic pollutants in the environment. Since degradation processes are commonly accompanied by isotope effects, monitoring the isotope composition of the studied compounds may provide insight on in-situ degradation processes. Analytical CSIA methods are well established for ca. 20 years for common organic pollutants, yet commercial solutions as GC-IRMS are restricted for measuring mostly ¹³C/¹²C, ¹⁵N/¹⁴N, and ²H/¹H isotope ratios. Chlorine isotope analysis (³⁷Cl/³⁵Cl), on the other hand, lacks a commercial solution, and requires alternative analytical strategies. In recent years, different online chlorine-CSIA techniques for chlorinated organic compounds were introduced. The two most commonly applied methods are based on the hyphenation of a gas-chromatograph (GC) to an isotope-ratio mass-spectrometer (IRMS), or to a quadrupole mass-spectrometer (qMS). A third instrument for chlorine isotope analysis to mention, which till date received only little attention, is a GC hyphenated to a multi-collector inductively coupled plasma mass-spectrometer (MC/ICPMS). Of these three, the high availability of GC/MS makes it an excellent tool for this task. In my talk I will explain the principles of using a GC/MS for measuring chlorine isotope ratios, and provide examples for its application in biodegraded and field samples.