Chapter 8: Spray Desorption Collection and DESI Mechanisms

The real-time in-line microlocalized-desorption sample processing that takes place during ambient ionization are of general analytical use, in addition to their utility during in direct analysis mass spectrometry. By decoupling the microlocalized-desorption sample-processing steps from direct analysis many benefits are realized, such as separate optimization capabilities for desorption and ionization. By using these novel sample-processing steps benefits are also realized over traditional sample-preparation procedures, such as solvent extraction, or swabbing for surface collection. The chapter illustrates how the decoupled desorption procedure can be used to obtain detailed information about the overall mechanism of the ambient ionization methods, illustrated by application to desorption electrospray ionization (DESI), as an example. It is shown that the desorption and ionization aspects of DESI respond differently to changes in operational conditions. This information will help practitioners of ambient ionization to select appropriate conditions for their analyses. In addition, applications of the spray desorption collection (SDC) technique are shown for analyses other than direct mass spectrometry.