Spraying Mode Effect on Droplet Formation and Ion Chemistry in Electrosprays

Depending on the spraying conditions and fluid properties, a variety of electrospray regimes exists. Here we explore the changes in ion production that accompany the transitions among the three axial spraying modes, the burst mode, the pulsating Taylor cone mode, and the cone-jet mode. Spray current oscillation and phase Doppler anemometry measurements, fast imaging of the electrified meniscus, and mass spectrometry are utilized to study the formation, size, velocity, and chemical composition of droplets produced in the three modes. High-speed images indicate that the primary droplets are produced by varicose waves and lateral kink instabilities on the liquid jet emerging from the Taylor cone, whereas secondary droplets are formed by fission. Dramatic changes in the droplet size distributions result from the various production and breakup mechanisms observed at different emitter voltages and liquid flow rates. We demonstrate that droplet fission can be facilitated by space charge effects along the liquid jet and in the plume. Compared to the other two regimes, a significantly enhanced signal-to-noise ratio, a lower degree of analyte oxidation, and milder fragmentation are observed for the cone-jet mode.

GIF Image

• ac062382isi20061217_055021.gif (1.1 MB)
• ac062382isi20061217_055124.gif (1.62 MB)
• ac062382isi20061217_055152.gif (459 KB)

Electronic Supporting Information files are available without a subscription to ACS Web Editions. All files are copyrighted by the American Chemical Society. Files may be downloaded for personal use only. Users are not permitted to reproduce, republish, redistribute, or resell any Supporting Information, either in whole or in part, in either machine-readable form or any other form without permission from the American Chemical Society. For permission to reproduce this material, requesters must process their own requests via the Rightslink permission system. Information about how to use the Rightslink permission system can be found at http://pubs.acs.org/page/copyright/permissions.html. Please read only the part about Rightslink.