9. Matrix-Assisted Laser Desorption and Ionization

Abstract

The chapter offers information on matrix-assisted laser desorption and ionization (MALDI), which is the most successful solid-state biopolymer ion source. The evolutionary process leading to MALDI began in the 1970s, with the introduction of the plasma desorption solid-state ion source. In this ion source, a peptide sample was deposited on a thin metal film by drying a few microliters of a peptide solution. MALDI has the capability of selectively producing ions representative of a mixture of biopolymer molecules present at a concentration of one micromolar in the presence of other organic and inorganic ions and molecules at one million-fold higher concentrations. The chapter outlines the development of solid-state ion sources for biopolymer analysis. Tandem mass spectrometry techniques have also been employed to gain sequence information from peptide and protein ions formed using MALDI. There have been numerous reports of the investigations of MALDI for the mass spectrometric analysis of oligonucleotides. MALDI has several advantages over other techniques for the analysis of synthetic polymers. It allows for the generation of intact, high mass polymer ions, which can be detected with minimal mass discrimination using time-of-flight (TOF) mass analyzers. With the use of Fourier transform mass spectrometry (FTMS), the limitations on mass accuracy and mass resolution of TOF mass analyzers can be overcome.