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ION COMPOSITION ELUCIDATION (ICE): A HIGH RESOLUTION MASS SPECTROMETRIC TECHNIQUE FOR IDENTIFYING COMPOUNDS IN COMPLEX MIXTURES
Citation:
Grange, A H. AND G W. Sovocool. ION COMPOSITION ELUCIDATION (ICE): A HIGH RESOLUTION MASS SPECTROMETRIC TECHNIQUE FOR IDENTIFYING COMPOUNDS IN COMPLEX MIXTURES. Presented at 17th Asilomar Conference on Mass Spectrometry, Pacific Grove, CA, October 19-23, 2001.
Impact/Purpose:
The research focused on in the subtasks is the development and application of state-of the-art technologies to meet the needs of the public, Office of Water, and ORD in the area of Water Quality. Located In the subtasks are the various research projects being performed in support of this Task and more in-depth coverage of each project. Briefly, each project's objective is stated below.
Subtask 1: To integrate state-of-the-art technologies (polar organic chemical integrative samplers, advanced solid-phase extraction methodologies with liquid chromatography/electrospray/mass spectrometry) and apply them to studying the sources and fate of a select list of PPCPs. Application and improvement of analytical methodologies that can detect non-volatile, polar, water-soluble pharmaceuticals in source waters at levels that could be environmentally significant (at concentrations less than parts per billion, ppb). IAG with USGS ends in FY05. APM 20 due in FY05.
Subtask 2: Coordination of interagency research and public outreach activities for PPCPs. Participate on NSTC Health and Environment subcommittee working group on PPCPs. Web site maintenance and expansion, invited technical presentations, invited articles for peer-reviewed journals, interviews for media, responding to public inquiries.
Subtask 3: To apply state-of-the-art environmental forensic techniques to the recognition and characterization of emerging pollutants in the aquatic environment. There is a need for high sensitivity and for a powerful method of structural characterization, advanced mass spectrometric and chromatographic techniques to be employed to meet the challenge of emerging pollutants, including pharmaceuticals and personal care products, agents of sabotage, and explosives. Ongoing efforts continue to identify previously unrecognized pollutants from a range of problematic samples having importance to regional and state contacts.
Subtask 4: To provide the Agency with a set of practical analytical methods for the selective and sensitive determination of selenium species (organic, inorganic, volatile and non volatile forms) in multiple media to accurately assess and if necessary control the risk of selenium exposure to organisms. This includes development of optimal extraction, digestion, separation and detection approaches.
Subtask 5: To develop and apply an analytical method that can extract and detect synthetic musks. The extent of exposure may be determined by measuring levels of synthetic musks from their potential source (communal sewage effluent). This subtask ends in FY05 with the deliverable of APM 21. Future applications to biosolids will be covered in subtask 6.
Subtask 6: Application, and improvement, of previously in-house developed sensitive, robust, and green, methodologies regarding the use of urobilin and sterols as a possible markers of sewage contamination.
Subtask 7: Adaptation and improvement of previously developed in-house methods, for PPCPs (e.g., antibiotics and musks) to solid materials (e.g. biosolids, sediments).
Subtask 8: Study of the presence of personal care products, incombustible organic compounds from the direct-piping of small engines exhaust in Lake Tahoe, and lake deposition of airborne pollutants from industrial activity
Description:
When tentatively identifying compounds in complex mixtures using mass spectral libraries, multiple matches or no plausible matches due to a high level of chemical noise or interferences can occur. Worse yet, most analytes are not in the libraries. In each case, Ion Composition Elucidation (ICE) provides a means for identifying compounds. This poster illustrates an example of each problem and its solution.
Three Compound Identification Problems
Multiple Plausible Library Matches
The mass spectrum in Figure la is a background-subtracted mass spectrum for a compound in an extract of 12 L of effluent from a tertiary waste water treatment plant. Figures lb-g are NIST library matches over the same mass range. The isomers in parenthesis in Figure I also had similar NIST mass spectra. The compound that provided the mass spectrum was present in the extract at an ultra-trace level. Chemical noise, coelution of compounds in the complex extract, and septum and column bleed components generally result in background-subtracted mass spectra containing extraneous ions or lacking low-abundance ions expected from the analyte. Hence, none of the NIST library matches can be ruled out without additional data.