C60 Secondary Ion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Secondary ion mass spectrometry (SIMS) has seen increased application for high spatial resolution chemical imaging of complex biological surfaces. The advent and commercial availability of cluster and polyatomic primary ion sources (e.g., Au and Bi cluster and buckminsterfullerene (C-60)) provide improved secondary ion yield and decreased fragmentation of surface species, thus improving accessibility of intact molecular ions for SIMS analysis. However, full exploitation of the advantages of these new primary ion sources has been limited, due to the use of low mass resolution mass spectrometers without tandem MS to enable enhanced structural identification capabilities. Similarly, high mass resolution and high mass measurement accuracy would greatly improve the chemical specificity of SIMS. Here we combine, for the first time, the advantages of a C-60 primary ion source with the ultrahigh mass resolving power and high mass measurement accuracy of Fourier transform ion cyclotron resonance mass spectrometry. Mass resolving power in excess of 100 000 (m/Delta m(50%)) is demonstrated, with a root-mean-square mass measurement accuracy below 1 part-per-million. Imaging of mouse brain tissue at 40 mu m pixel size is shown. Tandem mass spectrometry of ions from biological tissue is demonstrated and molecular formulas were assigned for fragment ion identification.