Utility of three types of mass spectrometers for determining elemental compositions of ions formed from chromatographically separated compounds

Abstract

Concentration factors of 1000 and more reveal dozens of compounds in extracts of water supplies. Library mass spectra for most of these compounds are not available, and alternative means of identification are needed. Determination of the elemental compositions of the ions in mass spectra makes feasible searches of commercial and chemical literature that often lead to compound identification. Instrumental capabilities that constrain the utility of a mass spectrometer for determining ion compositions for compounds that elute from a chromatographic column are scan speed, mass accuracy, linear dynamic range, and resolving power. Mass peak profiling from selected ion recording data (MPPSIRD) performed with a double-focusing mass spectrometer provides the best combination of these capabilities. This technique provides unique ion compositions for ions of higher mass from compounds eluting from a gas chromatograph than can be obtained by orthogonal acceleration time-of-flight (oa-TOF) or Fourier transform ion cyclotron resonance mass spectrometry. Multiple compositions are usually possible for an ion with a mass exceeding 150 Da within the error limits of the mass measurement. The correct composition is selected based on measured exact masses of the mass peak profiles resulting from isotopic ions higher in mass by 1 and 2 Da and accurate measurement of the summed abundances of these isotopic ions relative to the monoisotopic ion. A profile generation model (PGM) automatically determines which compositions are consistent with measured exact masses and relative abundances. The utility of oa-TOF and double-focusing mass spectrometry using ion composition elucidation (MPPSIRD plus the PGM) are considered for determining ion compositions of two compounds found in drinking water extracts and a third compound from a monitoring well at a landfill. Published in 2002 by John Wiley & Sons, Ltd.

Assigning product ions from complex MS/MS spectra: The importance of mass uncertainty and resolving power

“…Several researchers have investigated requirements for hyphenating high-resolution mass spectrometry with modern separation techniques. For example, Grange and coworkers [38] have summarized the requirements for determining elemental compositions for compounds eluting from chromatographic columns. Our study, however, was mainly concerned with very difficult to resolve product ion spectra of high peak densities.…”

Current use of high-resolution mass spectrometry in the environmental sciences

“…Despite its excellent features, however, this technique has rarely been used for determination of organic contaminants [10,29]. Almost all applications deal with persistent organic pollutants and other priority GC-amenable compounds in environmental [30,31] and biological [32,33] samples. A few applications are focussed on doping and drug control [29,34,35].…”

Mass Spectrometry

“…For utilizing the full discriminating power of combined accurate mass and isotope pattern information, accurate masses of the M + 1 and M + 2 isotope peaks and their complete mass peak profile should be evaluated, as these peaks are composed of different ion species [94].…”