Ion Sources Derived from Electrospray Ionization

Several ionization techniques that are derived from ESI are described in the following sections. 

3 Fused Droplet Electrospray Ionization and Extractive Electrospray Ionization 

The predecessor of PI-ESI was ultrasonication-assisted spray ionization (UASI) [107, 108]. In that early version, one end of a sample capillary was dipped in the sample vial held in an ultrasonicator (frequency 40 kHz) while the other (tapered) end was placed close ( 3 mm) to the MS inlet. Although no electric potential was applied to the tapered end of the capillary, electrospray could be observed, and mass spectra of analytes with 

The charges, with the signs opposite to the sign of the electric potential applied to the MS inlet, accumulate on the liquid meniscus at the capillary outlet. This process is followed by the formation of a Taylor cone and Coulomb explosions which lead to the formation of fine droplets. The mechanism responsible for generation of charged droplets and ions in Pl-ESI appears to be similar to that found in the conventional ESI process (Section 2.4). 

2 New Ion Sources Derived from Laser Desorption/Ionization 

---