Extraction of chlorinated aliphatic hydrocarbons from groundwater at micromolar concentrations for isotopic analysis of chlorine

• Published in: Environmental pollution (1987) Vol. 113; no. 3; pp. 263 - 269
• Main Authors: Holt, B.D, Heraty, L.J, Sturchio, N.C
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2001; Elsevier
• Subjects: 08 HYDROGEN; AIR; Analysis methods; Applied sciences; CARBON; CARBONATES; CHLORINATED ALIPHATIC HYDROCARBONS; CHLORINE; Chlorine Compounds - analysis; Chlorine isotope analysis; Environmental Monitoring - methods; Exact sciences and technology; EXTRACTION; FRACTIONATION; GROUND WATER; Hydrocarbons - analysis; HYDROGEN; Hydrogen-Ion Concentration; ISOTOPE RATIO; ISOTOPES; Isotopes - chemistry; Natural water pollution; Pollution; Sodium Hydroxide; Soil Pollutants - analysis; WATER; Water Pollutants, Chemical - analysis; Water treatment and pollution; Water; Extraction; Chlorinated aliphatic hydrocarbons; Chlorine isotope analysis; Trace analysis; Isotopic analysis; Chemical analysis; Aliphatic compound; Organochlorine compounds; Chlorine Organic compounds; Water pollution; Organic compounds; Chlorine 37; Ground water
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/S0269-7491(00)00191-3

Chlorine isotopic ratio techniques are used to characterize low molecular weight (solvent) hydrocarbons in groundwaters. A method is described for near-quantitative extraction of micromolar concentrations of chlorinated aliphatic hydrocarbons (CAHs) from water for determination of chlorine (Cl) isotope ratios. A low pressure, carrier-gas procedure of extraction was proven to be applicable to CH 2Cl 2, CCl 4, C 2H 2Cl 2, and C 2HCl 3. The pH of the water was adjusted with NaOH to prevent extraction of CO 2 from air and/or dissolved inorganic carbonate species. Recoveries of CAH samples (∼15 μmol), added to and extracted from ∼340 ml of water, averaged ∼96%. Average changes in the δ 37Cl values of the CAHs, attributable to the extraction process, were −0.01±0.06‰. Significant isotopic fractionation of Cl was measured during partial extraction of C 2CHCl 3 from water, indicating that near-quantitative extraction is required for reliable stable Cl isotope analysis of CAHs. This method is also suitable for the extraction of dissolved CAH for gas chromatography-combustion-isotope ratio mass spectrometric measurements of hydrogen and carbon.