How Are Completely Desolvated Ions Produced in Electrospray Ionization: Insights from Molecular Dynamics Simulations

Abstract

We apply molecular dynamics (MD) simulations to study the final phase of electrospray ionization (ESI), where an ion loses all of its associated solvent molecules. By applying an electric field to a cluster of H(2)O molecules solvating an ion and including a surrounding gas of varying pressure, we demonstrate that collisions with the gas play a major role in removing this final layer of solvent. We make quantitative predictions of the critical velocity required for the cluster to start losing molecules via collisions with gas and propose that this should be important in real ESI experiments. Such collisions have heretofore not been explicitly considered in discussions of the ESI process.

A Mechanism for Ionization of Nonvolatile Compounds in Mass Spectrometry: Considerations from MALDI and Inlet Ionization

“…We have shown a similar result with sonic spray ionization where a surface obstruction greatly increased the observed ion abundances [24,80]. Recent molecular dynamics simulations also suggests the importance of collisions for desolvation in ESI [81]. With typical AP and IP MALDI instruments, desolvation of the matrix with release of bare analyte ions can occur anywhere before the mass analyzer without affecting the mass measurement accuracy.…”

Lithium Ion–Water Clusters in Strong Electric Fields: A Quantum Chemical Study

“…[4][5][6][7][8] The behaviour of hydrated ions under intense electric fields is also important in electroporation of biological membranes 9-11 as well as in "bridging" transitions at interfaces separating media with different dielectric permittivities 12 which are relevant to electrospinning processes. 13 Electrospinning is becoming increasingly important, given its applicability in nanofiber manufacturing, drug delivery and tissue engineering.…”

Molecular Dynamics Simulations on Evaporation of Droplets with Dissolved Salts

“…The evaporation of droplets of dissolved salts (aqueous droplets) has extensive applications in many industrial processes such as crystallization [2,18], electrospraying [19], electrospinning [20], and atmospheric science [21][22][23][24][25]. Starov and Churaev [2] investigated the crystallization process of aqueous solutions in a thin capillary using hydrodynamics, and they presented that the evaporation flux differs significantly from that predicted by the classical solution with a one-component liquid.…”

“…Starov and Churaev [2] investigated the crystallization process of aqueous solutions in a thin capillary using hydrodynamics, and they presented that the evaporation flux differs significantly from that predicted by the classical solution with a one-component liquid. Recently, some studies have used molecular dynamics simulations to investigate the evaporation of a small water cluster dissolving a single kind of charged ion [19,[26][27][28]. Caleman and Spoel [26] simulated the evaporation from a water cluster (N = 216 and 512) containing either Cl Cann's results demonstrated that the interaction between ions and water molecules affects the evaporation of the cluster [19,27].…”

“…Recently, some studies have used molecular dynamics simulations to investigate the evaporation of a small water cluster dissolving a single kind of charged ion [19,[26][27][28]. Caleman and Spoel [26] simulated the evaporation from a water cluster (N = 216 and 512) containing either Cl Cann's results demonstrated that the interaction between ions and water molecules affects the evaporation of the cluster [19,27]. Kӧhler [21] investigated the process of formation of liquid cloud drops based on equilibrium thermodynamics, where water vapor condensed with existence of nucleus (solutes), and proposed the well-known Kӧhler theory expressed as:…”