Biological tissue imaging with a hybrid cluster SIMS quadrupole time-of-flight mass spectrometer

A 20 keV C60+ ion source was mounted onto a commercial MALDI/electrospray orthogonal ToF mass spectrometer. Cross-sectional mouse brain and lung slices between 5 and 10 μm prepared by cryostat sectioning were successfully imaged using a DC C60+ primary ion beam at a spot size of 100 μm. Analysis was performed at room temperature following vacuum drying. An abundance of ions were mapped in all samples, many whose identity can only be found using the MS/MS functionality. We have successfully identified and imaged localizations of diacylglycerol (DAG) ions – 1-palmitoyl-2-oleoyl-glycerol (m/z+ 577.5) and 1,2-dioleoyl-glycerol (m/z+ 603.5) – in lung tissue. The mouse brain slice revealed strong, distinct localizations of many ions revealing the potential for this technique for biological imaging. Ions throughout the mass range of m/z+ 50–800 were collected in sufficient quantities to permit unambiguous chemical mapping. Mass resolutions of 12,000 or greater were routinely obtained allowing for more accurate ion mapping than typically seen with ToF-SIMS image analysis.