Experimental methods to alleviate ion coupling effects in matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry

✍ Scribed by J. Scott Anderson; David A. Laude

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 861 KB
• Volume: 157-158
• Category: Article
• ISSN: 0168-1176
• DOI: 10.1016/s0168-1176(96)04405-9

✦ Synopsis

In Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry performed at high ion densities, coulombic interactions between ions of similar cyclotron frequencies may lead to coupled cyclotron motions. For ions residing in these modes, a coalescence of closely spaced ion frequencies will result, and the observed spectral line shape of otherwise distinct ion masses has the appearance of a single resonant cyclotron frequency. In this work, we use matrix-assisted laser desorption generated ions to provide examples of ion coupling and its effects on isotopic information. Two separate FT-ICR pulse sequences which alter the applied trap potentials are demonstrated to reverse the effects of ion coupling by reducing the ion density inside the trapped-ion cell. The result is a mass spectrum with a resolved isotopic envelope for previously coupled ion frequencies. Analytical benefits obtained with these pulse sequences when applied to a gramicidin-Dubos sample include a 300% increase in mass resolution and 100% improvement in mass measurement accuracy in the MALDIET-ICR spectrum.