Science Inventory

AUTOMATED DECONVOLUTION OF COMPOSITE MASS SPECTRA OBTAINED WITH AN OPEN-AIR IONIZATIONS SOURCE BASED ON EXACT MASSES AND RELATIVE ISOTIPIC ABUNDANCES

Citation:

GRANGE, A. H. AND G. SOVOCOOL. AUTOMATED DECONVOLUTION OF COMPOSITE MASS SPECTRA OBTAINED WITH AN OPEN-AIR IONIZATIONS SOURCE BASED ON EXACT MASSES AND RELATIVE ISOTIPIC ABUNDANCES. Presented at 2008 Pittsburgh Conference, New Orleans, LA, March 01 - 07, 2008.

Impact/Purpose:

Land Preservation and Restoration - by providing state-of-the-science chemical methods (encompassing sampling, preparation, separation, detection, and interpretation) to allow rapid and accurate field and laboratory analyses of contaminated soils, sediments, biota, and groundwater to support Superfund and hazardous waste clean-up decisions.

Description:

Chemicals dispersed by accidental, deliberate, or weather-related events must be rapidly identified to assess health risks. Mass spectra from high levels of analytes obtained using rapid, open-air ionization by a Direct Analysis in Real Time (DART®) ion source often contain

precursor, oxide, adduct, and/or dimeric ions. Ion compositions must be determined and ion

correlations must be made to understand composite mass spectra and enhance confidence in

tentative identifications. These tasks are performed rapidly by an in-house Ion Correlation

Program (ICP) that considers exact masses and relative isotopic abundances measured by a JEOL

AccuTOF® time-of-flight mass spectrometer. ASCII files provided by the data system acquired

at three CID voltages are imported into the ICP. Possible precursor ions and related oxidized,

ammonium adducts, protonated dimers, and ammoniated dimers are found in the lowest CID

voltage mass spectrum. At the intermediate CID voltage, dimeric ions are fragmented, while

possible precursor ions remain and are confirmed as such. Product ions are gleaned from the

highest CID voltage spectrum. Starting with the highest-mass precursor ion, all lower-mass ions

that are not precursor ions are checked to see if they are precursor ion subunits. When multiple

compounds are present with different collections of heteroatoms, some will and some will not

correlate with each precursor ion. Examples of mass spectra deconvolution will be demonstrated

for data acquired with the DART/TOFMS.

Record Details:

Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Product Published Date: 03/07/2008
Record Last Revised: 07/02/2008
OMB Category: Other
Record ID: 176545

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL EXPOSURE RESEARCH LABORATORY

ENVIRONMENTAL SCIENCES DIVISION

ENVIRONMENTAL CHEMISTRY BRANCH