Electrospray Ionization Time-Of-Flight Mass Spectrometer for Elemental Analysis

Abstract

Electrospray ionization (ESI) has been combined with a time-of-flight (TOF) mass spectrometer for elemental analysis. With the use of a heated-capillary interface, the instrument is shown to be stable to within 5% relative standard deviation (RSD) over a 60-min period. The ratio between the isotopes of rubidium is measured with a precision of 0.4% RSD for a 1-min integration time. With the addition of a supporting electrolyte as a spray stabilizer and internal standard, the dynamic range is linear over at least three orders of magnitude. The extent of solvent-cluster fragmentation is found to be governed primarily by the voltage differential between the capillary and skimmer and, to a lesser extent, by the capillary temperature. The capillary voltage also affects the distribution of species among the parent and its fragment ions for ferrocene and tetraethyllead. Under “mild” interface conditions, a resolving power of 1400 is achieved for an organolead complex. A spectrum for a larger molecule, polypropylene glycol, is presented to show the versatility of the ESI-TOF instrument for both atomic and molecular analysis.