Mass
spectrometry imaging by use of continuous-flow liquid microjunction
sampling at discrete locations (array mode) has previously been demonstrated.
In this Letter, we demonstrate continuous-flow liquid microjunction
mass spectrometry imaging of proteins from thin tissue sections in
raster mode and discuss advantages (a 10-fold reduction in analysis
time) and challenges (suitable solvent systems, data interpretation)
of the approach. Visualization of data is nontrivial, requiring correlation
of solvent-flow, mass spectral data acquisition rate, data quality,
and liquid microjunction sampling area. The latter is particularly
important for determining optimum pixel size. The minimum achievable
pixel size is related to the scan time of the instrument used. Here
we show a minimum achievable pixel size of 50 μm (<i>x</i>-dimension) when using an Orbitrap Elite; however a pixel size of
600 μm is recommended in order to minimize the effects of oversampling
on image accuracy
