Artifacts in Amine Analysis from Anodic Oxidation of Organic Solvents upon Electrospray Ionization for Mass Spectrometry

Abburi, Ramarao; Kalkhof, Stefan; Oehme, Ramona; Kiontke, Andreas; Birkemeyer, Claudia

doi:10.1255/ejms.1187

Cited by 9 publications

(16 citation statements)

References 32 publications

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“…Despite all of the above advances, there are still some areas in which better knowledge of electrochemical processes taking place in the electrospray capillary will be necessary to properly analyze obtained data (e.g., see a recent example pertaining to anodic oxidation of phenylenediamines during electrospray [138]). Studies of the kinetics of redox reactions are also possible, but they can quickly become quite complex: encompassing primary reactions occurring at the metal/solution interface as well as secondary chemical reactions, which in turn, may undergo electrochemical transformations that, yet again, engage in electron exchange.…”

Section: Discussionmentioning

confidence: 99%

Perspective on Electrospray Ionization and Its Relation to Electrochemistry

Pozniak

Cole

2015

J. Am. Soc. Mass Spectrom.

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A VAbstract. The phenomenon of electrospraying of liquids is presented from the perspective of the electrochemistry involved. Basics of current and liquid flow in the capillary and spray tip are discussed, followed by specifics of charging and discharging of the sprayed liquid surface. Fundamental theories and numerical modeling relating electrospray current to solution and spray parameters are described and then compared with our own experimentally obtained data. The method of mapping potentials and currents inside the electrospray capillary by using an inserted electrically-isolated small wire probe electrode is discussed in detail with illustrations from new and published data. Based on these experimentally obtained results, a new mathematical model is derived. The introduced "nonlinear resistor electrospray capillary model" divides the electrospray capillary into small sections, adds their contributions, and then, by transition to infinitely small section thickness, produces analytical formulas that relate current and potential maps to other properties of the electrospraying liquid: primarily conductivity and current density. The presentation of the model is undertaken from an elementary standpoint, and it offers the possibility to obtain quantitative information regarding operating parameters from typical analytical systems subjected to electrospray. The model stresses simplicity and ease of use; examples applying experimental data are shown and some predictions of the model are also presented. The developed nonlinear resistor electrospray capillary model is intended to provide a new quantitative basis for improving the understanding of electrochemical transformations occurring in the electrospray emitter. A supplemental material section gives full derivation of the model and discusses other consequences.

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Section: Discussionmentioning

confidence: 99%

Perspective on Electrospray Ionization and Its Relation to Electrochemistry

Pozniak

Cole

2015

J. Am. Soc. Mass Spectrom.

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“…deprotonation) or adduct formation (e.g. protonation) in the solution or gas phase [6], or by electrolytic oxidation or reduction [9,10]. The major steps of gas phase ion formation during the electrospray process are: (a) the production of charged droplets in the outlet of the capillary tip, (b) droplet disintegration to very small and highly charged droplets, due to evaporation of the solvent, and (c) the formation of gas phase ions.…”

Section: Introductionmentioning

confidence: 99%

Electrospray Ionization Efficiency Is Dependent on Different Molecular Descriptors with Respect to Solvent pH and Instrumental Configuration

et al. 2016

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Over the past decades, electrospray ionization for mass spectrometry (ESI-MS) has become one of the most commonly employed techniques in analytical chemistry, mainly due to its broad applicability to polar and semipolar compounds and the superior selectivity which is achieved in combination with high resolution separation techniques. However, responsiveness of an analytical method also determines its suitability for the quantitation of chemical compounds; and in electrospray ionization for mass spectrometry, it can vary significantly among different analytes with identical solution concentrations. Therefore, we investigated the ESI-response behavior of 56 nitrogen-containing compounds including aromatic amines and pyridines, two compound classes of high importance to both, synthetic organic chemistry as well as to pharmaceutical sciences. These compounds are increasingly analyzed employing ESI mass spectrometry detection due to their polar, basic character. Signal intensities of the peaks from the protonated molecular ion (MH+) were acquired under different conditions and related to compound properties such as basicity, polarity, volatility and molecular size exploring their quantitative impact on ionization efficiency. As a result, we found that though solution basicity of a compound is the main factor initially determining the ESI response of the protonated molecular ion, other factors such as polarity and vaporability become more important under acidic solvent conditions and may nearly outweigh the importance of basicity under these conditions. Moreover, we show that different molecular descriptors may become important when using different types of instruments for such investigations, a fact not detailed so far in the available literature.

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“…Successive formation of reactive oxygen species (such as H 2 O 2 (2OH À = H 2 O 2 + 2e À )) can also take place via electrolysis. [8] Obvious mass shift ( The anodic side reaction of analytes in positive-mode ESI has been well documented for alkylation and polymerization of phenylenediamines, [9,10] gas-phase methanol addition of aromatic aldehydes [11] and halogen addition to π-conjugated phosphasilenes. [12] Multiple electrochemical parameters, containing material of capillary metal, flow rate, needle voltage and gas flows, contribute to the reactions.…”

Section: Dear Sirmentioning

confidence: 99%

“…2(4)), indicating that the balance of gas parameter settings was one of controlling factors. On the other hand, no systematic trend was observed between the needle voltage setting and the relative intensities of oxygen addition peaks for terpendole E (1) (Supporting Information 6 (9) and 1,2,3,4-tetrahydrocarbazole (10) are favorable to take place at reactive C-2 and C-3 positions of indole. [15] To elucidate the oxidation site of terpendole E, MS/MS experiments were conducted on [M + H] + and the oxygen added peaks.…”

Section: Dear Sirmentioning

confidence: 99%

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Detection of oxygen addition peaks for terpendole E and related indole-diterpene alkaloids in a positive-mode ESI-MS

et al. 2014

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This report describes that a regular positive electrospray ionization mass spectrometry (MS) analysis of terpendoles often causes unexpected oxygen additions to form [M + H + O]+ and [M + H + 2O]+, which might be a troublesome in the characterization of new natural analogues. The intensities of [M + H + O]+ and [M + H + 2O]+ among terpendoles were unpredictable and fluctuated largely. Simple electrochemical oxidation in electrospray ionization was insufficient to explain the phenomenon. So we studied factors to form [M + H + O]+ and [M + H + 2O]+ using terpendole E and natural terpendoles together with some model indole alkaloids. Similar oxygen addition was observed for 1,2,3,4-tetrahydrocyclopent[b]indole, which is corresponding to the substructure of terpendole E. In tandem MS experiments, a major fragment ion at m/z 130 from protonated terpendole E was assigned to the substructure containing indole. When the [M + H + O]+ was selected as a precursor ion, the ion shifted to m/z 146. The same 16 Da shift of fragments was also observed for 1,2,3,4-tetrahydrocyclopent[b]indole, indicating that the oxygen addition of terpendole E took place at the indole portion. However, the oxygen addition was absent for some terpendoles, even whose structure resembles terpendole E. The breakdown curves characterized the tandem MS features of terpendoles. Preferential dissociation into m/z 130 suggested the protonation tendency at the indole site. Terpendoles that are preferentially protonated at indole tend to form oxygen addition peaks, suggesting that the protonation feature contributes to the oxygen additions in some degrees. © 2014 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons, Ltd.

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Artifacts in Amine Analysis from Anodic Oxidation of Organic Solvents upon Electrospray Ionization for Mass Spectrometry

Cited by 9 publications

References 32 publications

Perspective on Electrospray Ionization and Its Relation to Electrochemistry

Perspective on Electrospray Ionization and Its Relation to Electrochemistry

Electrospray Ionization Efficiency Is Dependent on Different Molecular Descriptors with Respect to Solvent pH and Instrumental Configuration

Detection of oxygen addition peaks for terpendole E and related indole-diterpene alkaloids in a positive-mode ESI-MS

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