Matrix-assisted laser desorption ionization and electrospray ionization combined with Fourier transform ion cyclotron resonance mass spectrometry

Paul O Staneke,Nico M M Nibbering

doi:10.1155/1997/406493

Abstract

During recent years, matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) are successfully employed to analyze biomolecules and polymers. In combination with Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry, high mass resolution and mass measurement accuracy can be achieved to enable the determination of molecular weights and structural characterization of biochemical compounds larger than 10 kDa.

Highlights

For a long time, efforts to analyze routinely large biomolecules by mass spectrometry were unsuccessful because commonly used ionization techniques, such as electron ionization, chemical ionization, field ionization, field desorption and fast atom bombardment could not produce the molecular ions of such compounds
With matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI), mass spectrometry can be used for the analysis of molecules with molecular weights of hundreds of kilodaltons whereas with the relatively harder ionization techniques the upper mass limit in routine applications was only a few kilodaltons
The successful application of mass spectrometry to analyze biomolecules and polymers has led to an increased application of MALDI and ESI over the last years

Summary

Introduction

Efforts to analyze routinely large biomolecules (molecular weights in excess of 10 kDa) by mass spectrometry were unsuccessful because commonly used ionization techniques, such as electron ionization, chemical ionization, field ionization, field desorption and fast atom bombardment could not produce the (quasi) molecular ions of such compounds. Laser desorption ionization (LDI) [1,2] has been achieved by illuminating a solid sample with a short intense light pulse This technique generates quasi-molecular ions, the efficiency is low and dependent on many variables. The technique is based on the principle that charged particles describe circular paths perpendicular to the direction of a uniform magnetic field and may be trapped for a variable period of time (ms to hours), whereby ions of interest may be selected by ejecting all other ions from the cell This is done by applying radio frequency pulses to ions with certain m/z ratios thereby increasing the kinetic energy of these ions and the radius of their circular orbits to such values that they are ejected from the cell. The ultra-high mass resolution provided by FT-ICR enabled the identification of their chemical formulas [22]

Combination of MALDI or ESI with FT-ICR

Conclusions