Simulated splashes: Elucidating the mechanism of desorption electrospray ionization mass spectrometry

Costa, Anthony; Cooks, R. Graham

doi:10.1016/j.cplett.2008.08.020

Cited by 184 publications

(176 citation statements)

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“…The first and best established is the droplet micro-extraction mechanism [25,26]. In this mechanism, initial droplets arriving at the surface form a localized and probably discontinuous liquid thin film, which dissolves analyte present on the surface.…”

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confidence: 99%

“…In this case, vaporization of the analyte from the surface is followed by fast charge-transfer reactions with protonated (or other) solvent molecules or droplets to produce charged analytes, which are then transferred into the mass spectrometer for mass analysis. A third mechanism, which also seems to make a limited contribution to ion production in DESI, involves reactive ion/surface collisions [25,27] sometimes known as chemical sputtering.In parallel with these advances in mechanistic understanding, surface and solvent systems used in DESI have been shown to have significant effects on ion intensity and several attempts have been made to identify improved systems. It is now understood that electrically nonconducting substrates increase ion signal in DESI experiments since they preserve charges by avoiding their neutralization [2,28].…”

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Enhanced ion signals in desorption electrospray ionization using surfactant spray solutions

Badu‐Tawiah

Cooks

2010

J. Am. Soc. Mass Spectrom.

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Solvent optimization is an important procedure in desorption electrospray ionization (DESI) and in this study the effects of solvent surface tension are explored. Data are presented for methanol/water/surfactant solvent systems, which show increases in ion signals of more than an order of magnitude when low concentrations of surfactants are added to the standard methanol/water (1:1) spray solvent. Examples of analytes tested include food chemicals, peptides, pharmaceuticals, and drugs of abuse. The improvement in ion intensity is mainly attributed to the effect of surface tension in producing smaller spray droplets, which are shown to cover a larger surface area. Surfactant-containing spray solutions allowed extension of DESI-MS analysis to previously intractable analytes like melamine and highly hydrophobic compounds like the sudan dyes. ( [3][4][5][6][7][8], which is used for surface sampling [9,10], high throughput analysis [11,12], and chemical imaging [13][14][15][16][17], largely because of its applicability to in situ analyte detection from unmodified surfaces. In DESI, a nebulized electrospray of high-velocity charged microdroplets is directed at a surface from which the solvent extracts analyte and carries it to the mass spectrometer in the form of secondary microdroplets. This methodology has been applied in a variety of disciplines including forensics [18,19], environmental science [20], food science [12,21], and pharmaceutical science [22]. With increased interest in ambient desorption mass spectrometry, the need has arisen to develop more versatile solvent systems that are applicable to a wider range of samples than is currently the case. One aspect of this effort is the use of non-aqueous spray solutions [23] and another is the addition of reagents to the spray solvent chosen to react and give ionic derivatives of the analytes of interest [24]. Both are discussed further below. In this work, we explore the special properties of spray solutions containing surfactants, in an attempt to increase the ion intensity and to learn more about the mechanisms of DESI.Three mechanisms have been identified in DESI, all falling under the rubric of droplet pick-up. The first and best established is the droplet micro-extraction mechanism [25,26]. In this mechanism, initial droplets arriving at the surface form a localized and probably discontinuous liquid thin film, which dissolves analyte present on the surface. Subsequent droplet-liquid-thin-film collisions produce secondary microdroplets containing the analyte, which are then sucked into the mass spectrometer for mass/charge analysis. A second mechanism is believed to involve gas-phase ion/molecule reactions [2]. In this case, vaporization of the analyte from the surface is followed by fast charge-transfer reactions with protonated (or other) solvent molecules or droplets to produce charged analytes, which are then transferred into the mass spectrometer for mass analysis. A third mechanism, which also seems to make a limited contribution to ion production in ...

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Enhanced ion signals in desorption electrospray ionization using surfactant spray solutions

Badu‐Tawiah

Cooks

2010

J. Am. Soc. Mass Spectrom.

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“…In DESI, a pneumatically-assisted electrospray produces charged droplets, which are directed at the surface of the sample, creating a thin liquid film which dissolves the analytes [68,69]. The impact of subsequent primary droplets releases secondary microdroplets containing analytes [68,69]. This so-called 'droplet pick-up' process is followed by the standard electrospray evaporation mechanisms which produce dry ions of the analytes [70,71].…”

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confidence: 99%

“…It is one of a group of ambient ionization methods [63][64][65] amongst which the laser-based method of laser ablation electrospray ionization (LAESI) [66,67] has given particularly useful images of biological systems, including in vivo systems. In DESI, a pneumatically-assisted electrospray produces charged droplets, which are directed at the surface of the sample, creating a thin liquid film which dissolves the analytes [68,69]. The impact of subsequent primary droplets releases secondary microdroplets containing analytes [68,69].…”

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Desorption electrospray ionization imaging mass spectrometry of lipids in rat spinal cord

Girod

Shi

Cheng

et al. 2010

J. Am. Soc. Mass Spectrom.

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Imaging mass spectrometry allows for the direct investigation of tissue samples to identify specific biological compounds and determine their spatial distributions. Desorption electrospray ionization (DESI) mass spectrometry has been used for the imaging and analysis of rat spinal cord cross sections. Glycerophospholipids and sphingolipids, as well as fatty acids, were detected in both the negative and positive ion modes and identified through tandem mass spectrometry (MS/MS) product ion scans using collision-induced dissociation and accurate mass measurements. Differences in the relative abundances of lipids and free fatty acids were present between white and gray matter areas in both the negative and positive ion modes. DESI-MS images of the corresponding ions allow the determination of their spatial distributions within a cross section of the rat spinal cord, by scanning the DESI probe across the entire sample surface. Glycerophospholipids and sphingolipids were mostly detected in the white matter, while the free fatty acids were present in the gray matter. These results show parallels with reported distributions of lipids in studies of rat brain. This suggests that the spatial intensity distribution reflects relative concentration differences of the lipid and fatty acid compounds in the spinal cord tissue. The "butterfly" shape of the gray matter in the spinal cord cross section was resolved in the corresponding ion images, indicating that a lateral resolution of better than 200 m was achieved. The selected ion images of lipids are directly correlated with anatomic features on the spinal cord corresponding to the white and the gray

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Desorption Electrospray Ionization Mass Spectrometry

Pasilis

2010

Encyclopedia of Analytical Chemistry

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Desorption electrospray ionization is an atmospheric pressure surface sampling/ionization technique for mass spectrometry. Desorption electrospray ionization consists of a pneumatically assisted electrospray ionization source, or emitter, held at a fixed angle above a sample surface. A high‐velocity spray consisting of charged solvent microdroplets in a gas stream emerges from the source and impacts the sample surface. The spray solubilizes any analyte molecules that are present and creates charged analyte‐containing secondary droplets that are drawn into the inlet of the mass spectrometer through an atmospheric pressure interface. Ionization may occur in a fashion similar to that involved in electrospray ionization, although other ionization mechanisms may also play a role. Analytes that can be detected using electrospray ionization mass spectrometry can also be detected using desorption electrospray ionization mass spectrometry. Desorption electrospray ionization can be used to rapidly sample surfaces ranging from living tissues to metal oxides for a diverse variety of analytes, and has been used for such important applications as direct determination of analytes present in complex matrices, analyses of biological tissues and forensically relevant materials, readout of thin‐layer chromatography plates, and chemical imaging. As in electrospray ionization, multiply‐charged ions are formed during desorption electrospray ionization, allowing for the detection of analytes having molecular weight ranges beyond the m / z range of the mass analyzer.

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Simulated splashes: Elucidating the mechanism of desorption electrospray ionization mass spectrometry

Cited by 184 publications

References 57 publications

Enhanced ion signals in desorption electrospray ionization using surfactant spray solutions

Enhanced ion signals in desorption electrospray ionization using surfactant spray solutions

Desorption electrospray ionization imaging mass spectrometry of lipids in rat spinal cord

Desorption Electrospray Ionization Mass Spectrometry

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