About the Electrospray Ionization Source in Mass Spectrometry: Electrochemistry and On-chip Reactions

Abstract

The present work shows that the electrochemical properties of electrospray ionization (ESI) can be used to add functions to the process. As example, we show how the choice of the electrode material can be used to study interactions between metal ions and biomolecules in mass spectrometry (MS). In positive ionization MS, an electrospray device acts as anode, which implies oxidation reactions. Sacrificial electrodes (made of copper or zinc) are used to supply the electrospray current and to produce cations that are able to react on-line with compounds of interest. Thus, the interactions between copper ions and ligands or peptides were investigated by using a copper electrode. Another example is the in situ electrogeneration of a dinuclear zinc(II) complex for the mass tagging of phosphopeptides when working with a zinc electrode. In order to perform these reactions on the same microchip, a dual-channel microsprayer was used, where one channel was dedicated to the tag electrogeneration and the other to the infusion of a phosphopeptides solution. Finally, this dual-channel microsprayer was used to study complexation at liquid-liquid interfaces in biphasic ESI-MS, such as thioether crowns and lead ions or peptides and phospholipids complexes. These examples illustrate the use of electrochemistry and on-chip reactions in ESI-MS analysis.

LEPA: From Proteomics to Energy Conversion

“…When a sacrificial metallic electrode is used to induce the ESI, metallic ions, such as Cu + , can be gen erated if the electrode is an anode to tag the peptides. [32] With this principle, combin ing between Cu +/2+ and βamyloid peptide was studied, which is quite important for neurodegenerative disorders. [33] More re cently, we have used microchips to study the oxidation of biomolecules to develop an electrochemical redoxomics strategy.…”

“…By using a dualchannel microchip, phospho peptides can be tagged online in the Taylor cone of ESI. [32] When a multichannel mi crochip is used, tyrosine nitration can be performed online by introducing various reactants through several microchannels, and the nitrated peptides can be character ized by MS. Droplets of oil and water can tive electrons in the conduction band can react with the samples present on the sur face of semiconductors to induce insource redox reactions, and the reaction products can be directly analyzed by MS spectrom eter. With this principle, peptide insource oxidative fragmentation, disulfide bond insource reduction and cysteine insource tagging were realized to facilitate pro teomic analyses.…”

3D-Printed Microfluidic Nanoelectrospray Ionization Source Based on Hydrodynamic Focusing

“…These features, in turn, deteriorated the difficulties to integrate nESI emitters in microfluidic chips. 21,22 Alternatively, three-dimensional (3D) printing has shown potentials to ease hurdles in preparing nESI emitters. Fused deposition modelling (FDM) is the most widely used 3D printing methods, 23,24 and it constructs 3D spatial objects by deposing melted polymers in pre-specified layers.…”