Electrospray laser desorption ionization (ELDI) mass spectrometry for molecular imaging of small molecules on tissues

The use of an ambient ionization mass spectrometry technique known as electrospray laser desorption ionization mass spectrometry (ELDI/MS) for molecular imaging is described in this section. The technique requires little or no sample pretreatment and the application of matrix on sample surfaces is unnecessary. In addition, the technique is highly suitable for the analysis of hard and thick tissues compared to other molecular imaging methods because it does not require production of thin tissue slices via microtomes, which greatly simplifies the overall sample preparation procedure and prevents the redistribution of analytes during matrix desorption. In this section, the ELDI/MS technique was applied to the profiling and imaging of chemical compounds on the surfaces of dry plant slices. Analyte distribution on plant slices was obtained by moving the sample relative to a pulsed laser and an ESI capillary for analyte desorption and post-ionization, respectively. Images of specific ions on sample surfaces with resolutions of 250 μm were typically created within 4.2 h for tissues with sizes of approximately 57 mm × 10 mm.