Electrospray droplet impact

Fig. 8.9 DESI ion source showing an electrospray of charged droplets impacting the surface where the molecules of interest are present. Once detached, they enter the ion source shown of the mass spectrometer. (Used with permission of Prosolia, Inc., Indianapolis, IN, USA)...

Desorption Electrospray Ionization (DESI). DESI is a novel gentle ionization method for surface analysis (Figure 2.6).[19,20] Like classical ESI, it operates at atmospheric pressure. No sample preparation is required. A solvent passes through the capillary of the electrospray source charged droplets are produced (primary ions) and they are directed to a solid sample. Their impact with the surface causes sample molecules to be ionized and... 

The latest addition to DI methods is DESI [10]. It directs an aqueous spray from an electrospray apparatus onto the sample on a surface. In the process, the fast nebulizing gas jet transports the charged droplets and impacts the... 

Desorption electrospray ionization (DESI) is a variant of ESI [33]. Electrosprayed aqueous solvent, with charged droplets and solvent ions, is directed at the sample of interest at ambient conditions. The sample may be a native sample or an analyte placed on an insulating surface. The analyte is desorbed by the result of either sputtering or impact desolvation. Desorbed ions are transferred into the vacuum system via an ion transfer line and mass analyzed. Jackson et al. [33] used DESI to analyze PMMA, poly (alpha-methyl styrene), and other polymers. 

The first publication on desorption electrospray ionization mass spectrometry (DESI-MS) appeared in 2004 (1). That paper has been followed by a stream of publications on a variety of atmospheric pressure surface sampling/ionization techniques for mass spectrometry (2). The popularity of DESI can be owed to its ease of use. In DESI, charged solvent droplets from a pneumatically assisted electrospray ionization source impact the surface to be analyzed, desorbing and ionizing analytes. The gas-phase analyte ions are then collected and transferred into the inlet of the mass spectrometer either directly or by using a transfer tube. 

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