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DETERMINATION OF ELEMENTAL COMPOSITIONS BY HIGH RESOLUTION MASS SPECTROMETRY WITHOUT MASS CALIBRANTS
Citation:
Grange, A H. AND G W. Sovocool. DETERMINATION OF ELEMENTAL COMPOSITIONS BY HIGH RESOLUTION MASS SPECTROMETRY WITHOUT MASS CALIBRANTS. Presented at American Society for Mass Spectrometry, 47th Annual Meeting, Dallas, TX, June 13-17, 1999.
Description:
Widely applicable mass calibrants, including perfluorokerosene, are available for gas-phase introduction of analytes ionized by electron impact (EI) prior to analysis using high resolution mass spectrometry. Unfortunately, no all-purpose calibrants are available for recently developed liquid sample introduction techniques that use electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI). ESI and APCI generally provide less sensitivity than EI ionization and a portion of the weaker total signal must arise from calibrant ions. Solvent conditions must be found that provide ions from both the calibrant and analytes, or an alternative flow to the ionization region must be provided for the calibrant solution. However, even without mass calibrants, relative abundances of ions, the presence of multiple mass peak profiles from an analyte at a single nominal mass, and exact mass differences between ions are determinable. These data alone were used to establish elemental compositions of several compounds. Seven solutions, each containing a different standard with a concentration of 10 ng/uL in 1:1 methanol: water with 1% acetic acid, were infused at 2 to 8 uL/min into an ESI source without addition of mass calibrants. Infusion was required to provide a lock mass for the lowest mass ion monitored in each Mass Peak Profiling from Selected Ion Recoding Data (MPPSIRD) experiment. The elemental compositions of the protonated molecular ion and fragment ions from each standard were determined. This approach could be useful for identifying compounds in chromatographic fractions.