European Journal of Mass Spectrometry - Abstract of Application and evaluation of solvent-free matrix-assisted laser desorption/ionization mass spectrometry for the analysis of derivatized fullerenes

Sotirios G. Kotsiris,^a Yury V. Vasil’ev,^a,b Alexey V. Streletskii,^a Ming Han,^a Lewis P. Mark,^a Olga V. Boltalina,^c Nikos Chronakis,^d Michael Orfanopoulos,^e Hartmut Hungerbühler^f and Thomas Drewello^a,*
^aDepartment of Chemistry, University of Warwick, Coventry CV4 7AL, UK. E-mail: T.Drewello@warwick.ac.uk
^bDepartment of Physics, Bashkir State Agricultural University, Ufa, Russia
^cDepartment of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
^dDepartment of Chemistry, University of Cyprus, Nicosia 1678, Cyprus
^eDepartment of Chemistry, University of Crete, Heraklion 71409, Crete, Greece
^fFachbereich II Pharma- und Chemietechnik, Technische Fachhochschule Berlin, Berlin, Germany

A variety of derivatized fullerenes have been studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Of particular emphasis has been the evaluation of a recently introduced solvent-free sample/target preparation method. Solvent-free MALDI is particularly valuable in overcoming adverse solvent-related effects, such as insolubility and/or degradation of the sample. The method was applied to fullerene derivatives susceptible to decomposition under insufficiently “soft” MALDI conditions. Analytes included the hydrofullerene: C₆₀H₃₆, fluorofullerenes: C₆₀F_x where x = 18, 36, 46, 48 and C₇₀F_x where x = 54, 56, methano-bridged amphiphilic ligand adducts to C₆₀ and the [4 + 2] cycloadduct of tetracene to C₆₀. The new solvent-free sample preparation is established as an exceedingly valuable addition to the repertoire of preparation protocols within MALDI. The MALDI mass spectra were of very high quality throughout, providing a testimony that “soft” MALDI conditions could be achieved. Using the [4 + 2] cycloadduct of tetracene to C₆₀ as the model analyte for direct comparison with solvent-based MALDI, the solvent-free approach led to less fragmentation and more abundant analyte ions. Applying solvent-free sample preparation, different matrix compounds have been examined for use in the MALDI of derivatized fullerenes, including sulfur, tetracyanoquinodimethane (TCNQ), 9-nitroanthracene (9-NA) and trans-2-[3-(4-tert- butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB). DCTB was confirmed as the best performing matrix, reducing unwanted decomposition and suppression effects.