The role of surface in desorption electrospray ionization-mass spectrometry: advances and future trends
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FEATURE ARTICLE
The role of surface in desorption electrospray ionization-mass spectrometry: advances and future trends Federica Bianchi 1 & Monica Mattarozzi 1 & Maria Careri 1 Received: 20 December 2019 / Revised: 12 March 2020 / Accepted: 17 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract An outlook on the current status and trends in desorption electrospray ionization-mass spectrometry (DESI-MS), one of the most common spray-based techniques for ambient ionization, is given with a focus on the main advances recently achieved or still in progress regarding studies of surface properties affecting the signal stability and efficiency of the DESI process. Future directions that the field may take in the years to come are discussed, with particular focus on bioanalytical research. Keywords Ambient mass spectrometry . Desorption electrospray ionization . Surface
Introduction Ambient mass spectrometry (AMS) represents an important addition to the bioanalytical toolbox. AMS techniques involve analyte sampling and ionization under atmospheric pressure, enabling the recording of mass spectra on ordinary samples in their native environment, with no or minimal sample preparation [1, 2]. Among ambient MS techniques, desorption electrospray ionization (DESI) employs a stream of small charged droplets to locally dissolve analytes from a solid surface, forming first a thin liquid layer when the surface is bombarded by the solvent spray plume and then gas-phase analyte ions, generated by an electrospray (ESI)-like mechanism, which can be sampled in a mass spectrometer. As in the case of other AMS methods, desorption and ionization occur externally from the mass spectrometer in the open environment. Since ionization occurs according to an electrospray-like mechanism, DESI enables the spectra of small molecules, as well as proteins and other biological compounds, to be recorded under ambient conditions, and is applicable to solid samples, liquids, frozen solutions and adsorbed gases. While traditional DESI addresses solid or dried samples deposited onto * Maria Careri [email protected] 1
Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Parco Area delle Scienze 17/A, 43124 Parma, Italy
a surface, the technique has been subsequently extended to analysis of liquid samples that are transferred through a fused silica capillary for ionization. Investigations into the DESI mechanism have been performed using a variety of strategies [1, 3–7]. A droplet pickup model requiring the solvent to make contact with the surface and other mechanisms have been hypothesized to be involved in the DESI ionization of polar biomolecules like peptides and proteins as model compounds: primary and secondary droplet sizes and velocities were measured as a function of operating conditions such as nebulizing supply pressure and distance between the sprayer tip and surface. Both these factors were shown to have a large effect on the velocities of the droplets and on the
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