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Environ Sci Technol

Title:		(13)C/(12)C analysis of ultra-trace amounts of volatile organic contaminants in groundwater by vacuum extraction
Author(s):		Amaral HI; Berg M; Brennwald MS; Hofer M; Kipfer R;
Address:		"Swiss Federal Institute of Aquatic Science and Technology, 8600 Dubendorf, Switzerland. Helena.Amaral@ineti.pt"
Journal Title:		Environ Sci Technol
Year:		2010
Volume:		44
Issue:		3
Page Number:		1023 - 1029
DOI:		10.1021/es901760q
ISSN/ISBN:		0013-936X (Print) 0013-936X (Linking)
Abstract:		"We developed a method for the vacuum extraction (VacEx) of volatile organic compounds (VOCs) from water samples for ultratrace determinations of carbon isotopic signatures. Our method permits compound-specific stable carbon isotope analysis (CSIA) at VOC concentrations as low as 0.03-1.34 microg/L. VacEx was developed to extract and preconcentrate VOCs for subsequent carbon-CSIA by the standard technique purge-and-trap (P&T) coupled to an isotope-ratio mass spectrometer (IRMS). Even without complete extraction, the delta(13)C signatures of VOCs determined by VacEx-P&T-IRMS were in good agreement (deviation <1 per thousand) with signatures determined by P&T-IRMS. This indicates that VacEx does not cause isotopic discrimination. Limits of quantification (LOQs) for delta(13)C analysis were: 0.03-0.06 microg/L for benzene, toluene, o-xylene, m-p-xylene and ethylbenzene, 0.09 microg/L for methyl tert-butyl ether (MTBE), and 0.18-0.27 microg/L for trans-DCE, cis-DCE, TCE and PCE. These are the lowest LOQs reported to date for continuous-flow isotope-ratio determinations using a commercially available and automated system. To our knowledge, analytical protocols adopted from noble gas analysis in water were applied for the first time to determine the isotope composition of organic contaminants. We applied VacEx in a field study to illustrate how the determination of VOC isotopic signatures at very low concentrations opens new avenues in the in situ assessment of these priority groundwater pollutants"
Keywords:		"Carbon/chemistry Carbon Isotopes Environmental Monitoring/*methods Organic Chemicals/*chemistry Vacuum Water/*chemistry Water Pollutants, Chemical/*chemistry;"
Notes:		"MedlineAmaral, Helena I F Berg, Michael Brennwald, Matthias S Hofer, Markus Kipfer, Rolf eng 2010/01/01 Environ Sci Technol. 2010 Feb 1; 44(3):1023-9. doi: 10.1021/es901760q"