Discussion

Desorption Electrospray Ionization Mass Spectrometry (DESI-MS), the first ambient ionisation MS (AIMS) method is celebrating its 13th birthday in November 2015, which gives an opportunity to assess the significance and potential future role of these methods inside and outside of the boundaries of analytical chemistry. AIMS methods opened up a tremendous application space for mass spectrometry by lifting up the traditional constraints associated with obligatory sample preparation and chromatographic separation. The initial enthusiasm around DESI and DART (Direct Analysis In Real-Time) was attenuated soon by recognizing the intrinsic limitations of these methods regarding quantification or trace analysis. Nevertheless, a number of real-life applications have been developed together with a number of second- and third generation AIMS methods. Among the potential applications of DESI, MS imaging has emerged as a principal area, providing a more robust alternative to MALDI-MS. Although the chemical application range of DESI-MSI is limited to low molecular weight species, its medical diagnostic utility has been demonstrated to be excellent, especially on the field of cancer diagnostics and cancer patient stratification. In the light of the recent results, the technique is likely to find its application space in routine histopathology environment.