Taylor cones

Liquid Metal Sources. The source feed is a metal of low melting point - Ga and In are commonly employed. It is introduced as a liquid film flowing over a needle towards the tip whose radius is relatively blunt (10 pm). The electrostatic and surface tension forces form the liquid into a sharp point known as the Taylor cone. Here the high electric field is sufficient to allow an electron to tunnel from the atom to the surface, leaving the atom ionized. 

Figure 11.2 A schematic of the electrospray process, showing the release of charged droplets from the Taylor cone and the Z-spray arrangement with respect to the sample inlet, sample cone, and the subsequent path of the ions into the analyzer.

Fig. 11.11. Schematic of Taylor cone formation, ejection of a jet, and its disintegration into a fine spray. The electrochemical processes of ESI [77,78] are also assigned. Adapted from Ref. [49] by permission of the authors.

Fig. 11.12. Electrospray from a nanoESI capillary. The jet emitted from the Taylor cone is clearly visible and separate from the region of rapid expansion into a plume of microdroplets. By courtesy of New Objective, Woburn, MA.

Wdm, M.S. Mann, M. Electrospray and Taylor-Cone Theory, Dole s Beam of Macromolecules at Last Int. J. Mass Spectrom. lonProc. 1994,136, 167-180. 

Although previous studies showed that direct ionization from the outlet separation channel at the chip surface with Taylor cone formation could be possible, this is probably not optimal because the ESI cone volumes are larger than peak volumes. With short... 

In ESI MS, a dissolved sample is sprayed through a capillary in an electric field which is situated in front of the vacuum inlet of the mass spectrometer [2]. Thus, in contrast to most other ionization techniques performed in high vacuum, the ionizahon process takes place at the atmospheric pressure. After leaving the capillary, the solvent forms a so-called Taylor-cone, which further forms a filament and finally, the spray of small droplets (Figure 14.2). These droplets carry charges on the surface this is frequently supported by the acidification of the solvent. The droplets shrink is caused by the evaporation of the solvent. This leads to an increase of the charge-per-surface ratio, finally... 

M. S. Wilm and M. Mann, Electrospray and Taylor-cone theory, Dole s beam of macromolecules at last Int. J. Mass Spectrom. Ion Process., 136 (1994) 167-180. 

A typical solution present in the capillary consists of a polar solvent in which electrolytes are soluble. Low electrolyte concentrations, 10 5 to 10 3 mol 1, are typically used in ESMS. When turned on, the field Ec will penetrate the solution at the capillary tip and the positive and negative electrolyte ions in the solution will move under the influence of the field until a charge distribution results which counteracts the imposed field and leads to essentially field-free conditions inside the solution. When the capillary is the positive electrode, positive ions will have drifted downfield in the solution, i.e., toward the meniscus of the liquid, and negative ions will have drifted away from the surface. The mutual repulsion between the positive ions at the surface overcomes the surface tension of the liquid and the surface begins to expand, allowing the positive charges and liquid to move downfield. A cone forms, the so-called Taylor cone [19], and if the... 

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