Electrohydrodynamic ionization mass spectrometry - the ionization of liquid glycerol and non-volatile organic solutes

Simons, David S.; Colby, B. N.; Evans, C. A.

doi:10.1016/0020-7381(74)85006-0

Cited by 126 publications

(58 citation statements)

References 23 publications

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“…We note, however, that earlier vacuum electrospray studies conducted with glycerol solutions observed a multitude of solvated ions including metastable ions and multiply charged species. 3,31,32,103 In general, the emitted cluster ions recorded in the MD simulations contain more nascent formamide molecules (that is, they are characterized by larger solvation numbers) than the clusters observed in the experiments where typical flight times (that is, the elapsed time between the instant of cluster generation and the moment of its detection) are of the order of 30 µs. The recorded occurrence of larger solvated ion clusters is likely to be correlated with the propensity of the solvent (formamide) to form hydrogen bonds (see Figures 11c-e).…”

Section: Discussionmentioning

confidence: 96%

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that forms being characterized by high surface-normal electric field strengths in the vicinity of 1 V/nm. Mass-to-charge ratios were determined for both positive and negative currents sprayed from NaI−formamide solutions with solute−solvent mole ratios of 1:8.4 and 1:36.9, and from KI−formamide solutions with mole ratios of 1:41 and 1:83. The molecular dynamics simulations were conducted on isolated 10 nm NaI−formamide droplets at mole ratios of 1:8 and 1:16. The droplet was subjected to a uniform electric field with strengths ranging between 0.5 and 1.5 V/nm. Both the experiments and simulations demonstrate a mixed charge emission regime where field-induced desorption of solvated ions and charged droplets occurs. The macroscopic parameters, such as average mass-to-charge ratio and maximum surface-normal field strengths deduced from the simulations are found to be in good agreement with the experimental work and consistent with electrohydrodynamic theory of cone-jets. The observed mass spectrometric Na+ and I− solvated ion distributions are consistent with a thermal evaporation process, and are correctly reproduced by the simulation after incorporation of the different flight times and unimolecular ion dissociation rates in the analysis. Alignment of formamide dipoles and field-induced reorganization of the positive and negative ionic charges in the interfacial region are both found to contribute to the surface-normal field near the points of charge emission. In the simulations the majority of cluster ions are found to be emitted from the tip of the jet rather than from the neck region next to the Taylor cone. This finding is consistent with the experimental energy distributions of the solvated ions which demonstrate that indeed most ions are emitted closer to the jet region, that is, beyond the cone-neck region where ohmic losses occur. This observation is also consistent with continuum electrohydrodynamic predictions of cluster-ion evaporation at surface regions of high curvature and therefore maximum surface electric field strengths, which may be the cone-neck region, the breakup region of the jet (usually near the tip of the jet), or the emitted charged droplets. In the nanoscale jets observed in this study, the regions of highest spatial curvature are at the ends of the jets where nascent drops either are forming or have just detached. The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that form...

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Section: Discussionmentioning

confidence: 96%

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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“…Carrying out the electrospray ionization under the atmospheric pressure condition is advantageous compared with that in high vacuum because the ambient gas that surrounds the electrosprayed charged droplets acts as a heat bath, and can provide sufficient thermal energy to vaporize the volatile solvent without freezing the aerosol droplets [1,2]. This allows ESI to work with wide range of solvents including those used in the liquid chromatography, while its vacuum counterpart, electrohydrodynamic (EHD) spray could only handle lowvolatility solvents [3,4].…”

Section: Introductionmentioning

confidence: 99%

High Pressure (>1 atm) Electrospray Ionization Mass Spectrometry

Chen

Mandal

Hiraoka

2011

J. Am. Soc. Mass Spectrom.

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High pressure electrospray ionization mass spectrometry has been performed by pressurizing a custom made ion source chamber with compressed air to a pressure higher than the atmospheric pressure. The ion source was coupled to a commercial time-of-flight mass spectrometer using a nozzle-skimmer arrangement. The onset voltage for the electrospray of aqueous solution was found to be independent on the operating pressure. The onset voltage for the corona discharge, however, increased with the rise of pressure following the Paschen's law. Thus, besides having more working gas for the desolvation process, gaseous breakdown could also be avoided by pressurizing the ESI ion source with air to an appropriate level. Stable electrospray ionization has been achieved for the sample solution with high surface tension such as pure water in both positive and negative ion modes. Fragmentation of labile compounds during the ionization process could also be reduced by optimizing the operating pressure of the ion source.

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“…When the microchannels in a microporous membrane are made small enough, solution does not¯ow through the membrane but an electric ®eld can be used to extract precharged ions from a liquid sample. This experiment, which is a micro version of an ionization technique known as electrohydrodynamic ionization (Simons et al, 1974), has been performed with a 10 mm poly(ethylene terephthalate) membrane containing 10 7 micro (25±50 nm) diameter channels by applying an electric ®eld established using a potential of some hundreds of volts (Yakovlev et al, 1994). (compare Section VII.G)…”

Section: Membrane Introduction Mass Spectrometrymentioning

confidence: 99%