You are here:
CHARACTERIZATION OR IDENTIFICATION OF ORGANIC COMPOUNDS BY ION COMPOSITION ELUCIDATION (ICE) USING GAS CHROMATOGRAPHY/HIGH RESOLUTION MASS SPECTROMETRY
Citation:
Grange, A H. AND G W. Sovocool. CHARACTERIZATION OR IDENTIFICATION OF ORGANIC COMPOUNDS BY ION COMPOSITION ELUCIDATION (ICE) USING GAS CHROMATOGRAPHY/HIGH RESOLUTION MASS SPECTROMETRY. Presented at 18th Annual International Conference on Contamination in Soils, Sediments, and Water, Amherst, MA, October 21-24, 2002.
Impact/Purpose:
Provide state-of-the-science sampling, analysis, separation, and detection methods to allow rapid, accurate field and laboratory analyses of contaminated soils, sediments, biota, and groundwater to support Superfund clean-up decisions. Apply state-of-the-science methods in chemical analysis and data interpretation (e.g., mass spectral interpretation) to actual problems of OSWER, the Regions, and the States, in cooperation with the Las Vegas Technical Support Center as well as by direct contacts with Regional and State employees. Provide technical advice and guidance to OSWER using the environmental chemistry expertise (e.g., mass spectrometry, analytical methods development, clean-up methodology, inorganics, organometallics, volatile organics, non-volatile organics, semi-volatile organics, separation technologies, etc.) found within the branch.
Technical research support for various projects initiated either by Regions/Program Offices or ECB scientists. While these efforts will support the Regions and Program Offices, they cannot be predicted or planned in advance, and may serve multiple duty (e.g., solve real-world problems, serve to ground-truth analytical approaches that ECB is developing, transfer new technology). Many of the activities in this task support requests involving enforcement decisions and therefore are categorized as "environmental forensics".
Description:
Only a small fraction of the compounds found in contaminated sites and water supplies is found in mass spectral libraries or has known toxicological effects. The EPA lists 2800 high production volume chemicals. These compounds, byproducts, and degradation products might be found in drinking water sources, air, and contaminated sites. Identification of these compounds is necessary to assess risk to humans and aquatic ecosystems. Hence, there is a need for more powerful analytical techniques to identify such compounds. To limit tedious pre-analysis fractionations, compound identification techniques must isolate signals from low-level contaminants in complex mixtures. Excellent component separation is realized by high resolution gas chromatography (separation in time) coupled to high resolution mass spectrometry (selection by exact mass).
Ion Composition Elucidation (ICE) employs a software adaptation for double focusing mass spectrometers to measure the exact masses and relative abundances of the mass peak profiles of monoisotopic ions and the profiles higher in mass by 1 and 2 amu that arise from heavier isotopes such as 'IC, "N, 180, and "S. Three measured exact masses and two relative abundances are entered into a Profile Generation Model to provide the composition of the molecular ion or fragment ion. Tables of ion compositions limit the number of possible compounds that could produce the mass spectrum and make feasible library searches of chemical and commercial literature to reach tentative identifications. If a standard can be obtained, the tentative identification can be confirmed. If not, the compound can be tracked to its source using the compound's retention time and ion compositions, which provide greater specificity than a low resolution mass spectrum.
Two applications of ICE will be discussed: identification of isomeric compounds found in a municipal well that served Toms River, NJ, and characterization of two families of compounds found in Superfund sites - one chemical byproducts and one of microbial origin.