Electrospray mass spectrometry using potassium iodide in aprotic organic solvents for the ion formation by cation attachment

Saf, Robert; Mirtl, Christian; Hummel, Klaus

doi:10.1016/s0040-4039(00)73459-9

Cited by 32 publications

(13 citation statements)

References 9 publications

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“…4(a) and Series I in Fig. 4(b) have been observed in previous ESI studies of synthetic polymers 30,33 and are assigned as cluster peaks incorporating a solvent molecule, that is, [PS + Cat + DMF] + . Peaks that are due to ions formed because of salt contamination are also observed.…”

Section: Resultsmentioning

confidence: 62%

“…For ESI experiments, the polystyrene sample concentration was 5 mg/ mL in 50:50 tetrahydrofuran (THF) + dimethylformamide (DMF). 30 The mobile phase consisted of 50:50 DMF + THF and was pumped towards the tip of a stainless steel capillary at a flow rate of 30 µL/min. A Rheodyne injector fitted with a 20 µL loop was employed to inject the sample solution into the flow of the mobile phase.…”

Section: Sample Preparationmentioning

confidence: 99%

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A Study of Cation Attachment to Polystyrene by Means of Matrix-assisted Laser Desorption/Ionization and Electrospray Ionization-Mass Spectrometry

Deery

Jennings

Jasieczek

et al. 1997

Rapid Commun. Mass Spectrom.

105

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A range of metal cations has been shown, by means of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, to form adduct complexes with polystyrene. Both MALDI and ESI mass spectra contain adduct ion peaks corresponding to [ Polymers such as PEG and PMMA, which contain basic oxygen atoms in the repeat unit, interact effectively with alkali metal ions such as Li + and Na + . It has been shown, by means of molecular modelling calculations, that the lowest energy conformer structure of [PEG + Na] + (where the degree of polymerisation, n, is 9) involves multiple oxygen atoms which are coordinated about the Na + centre. 37 Conversely, polystyrene is a hydrocarbon and contains no basic atoms to which metal ions may bind. It is thought that the most likely site of cation attachment along the polystyrene chain is the phenyl ring in the repeat unit. 38Previous MALDI-MS studies have shown that the molecular weight (MW) distribution that is observed in the mass spectra of polar polymers is dependent on which alkali metal salt is used to dope the polymer and matrix mixture. [39][40][41][42] For example, it has been demonstrated that the value of the number-average molecular weight (M n ) (Eq 1) of PET 43 and PMMA 39 increases with increasing size of cation. It is thought that the larger cations (Rb + , Cs + ) have a more favourable interaction with higher molecular weight oligomers of these polymers, resulting in an apparent shift in the MW distribution.In the present study, both MALDI and ESI-MS are used with the aim of establishing which cations interact favourably with polystyrene and whether the observed molecular weight distributions vary with the cation used. EXPERIMENTAL Mass spectrometryAll ESI experiments were carried out in a Quattro II (Micromass, Manchester, UK) tandem quadrupole instrument (Q 1 hQ 2 , where h is a hexapole collision cell) fitted with an electrospray source. The sampling cone potentials used in this study ranged from 90 to 180 V. It was generally found that, as the cone potential was increased beyond 150 V, the signal-to-noise ratio of the polystyrene ions increased significantly. Despite the high potentials applied to the cone, no fragmentation of the molecular ions was observed in the mass spectra. The spectra, from which molecular weight average values were calculated, were all acquired with the cone potential set at 180 V. The first quadrupole was scanned from m/z 3000-500 for a total of 20-30 scans. Ions, mass analysed by Q 1 , were detected by the first scintillator detector to generate the mass spectrum. All data were processed by means of the MassLynx data system. MALDI experiments were carried out in a TofSpec (Micromass, Manchester, UK) time-of-flight (TOF) instrument operated in reflectron mode. Ions generated in the source region, by means of a nitrogen laser * Correspondence to: M. J. Deery

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Section: Resultsmentioning

confidence: 62%

Section: Sample Preparationmentioning

confidence: 99%

A Study of Cation Attachment to Polystyrene by Means of Matrix-assisted Laser Desorption/Ionization and Electrospray Ionization-Mass Spectrometry

Deery

Jennings

Jasieczek

et al. 1997

Rapid Commun. Mass Spectrom.

105

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show abstract

“…In positive ion ESI, analyte adducts with sodium, lithium, ammonium, or other cationic species are often observed. The addition of salts to yield these cations to samples of weakly basic or polar, neutral analytes can facilitate the formation of positive ions (Saf, Mirtl, & Hummel, 1994; Ackloo et al, 2000).…”

Section: Analyte Characteristics and Selectivitymentioning

confidence: 99%

Practical implications of some recent studies in electrospray ionization fundamentals

Cech

Enke

2001

Mass Spectrometry Reviews

1,268

1,299

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In accomplishing successful electrospray ionization analyses, it is imperative to have an understanding of the effects of variables such as analyte structure, instrumental parameters, and solution composition. Here, we review some fundamental studies of the ESI process that are relevant to these issues. We discuss how analyte chargeability and surface activity are related to ESI response, and how accessible parameters such as nonpolar surface area and reversed phase HPLC retention time can be used to predict relative ESI response. Also presented is a description of how derivitizing agents can be used to maximize or enable ESI response by improving the chargeability or hydrophobicity of ESI analytes. Limiting factors in the ESI calibration curve are discussed. At high concentrations, these factors include droplet surface area and excess charge concentration, whereas at low concentrations ion transmission becomes an issue, and chemical interference can also be limiting. Stable and reproducible non-pneumatic ESI operation depends on the ability to balance a number of parameters, including applied voltage and solution surface tension, flow rate, and conductivity. We discuss how changing these parameters can shift the mode of ESI operation from stable to unstable, and how current-voltage curves can be used to characterize the mode of ESI operation. Finally, the characteristics of the ideal ESI solvent, including surface tension and conductivity requirements, are discussed. Analysis in the positive ion mode can be accomplished with acidified methanol/water solutions, but negative ion mode analysis necessitates special constituents that suppress corona discharge and facilitate the production of stable negative ions.

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“…[10][11][12] Neutral compounds can be more difficult to ionize and are likely to form adducts with ions in solution such as NH 4 þ , Na þ , and K þ in the positive ion mode, or acetate, formate, and chloride in the negative ion mode. [13][14][15] Non-volatile salts such as phosphate buffers, and non-volatile inorganic acids such as sulfuric and phosphoric acid, should be avoided in ESI since they can crystallize in the ion source, cause corrosion, and produce complex mass spectra due to a variety of complexation reactions. Ionpairing reagents such as triethylamine (TEA) and trifluoroacetic acid (TFA) should be used in very low concentrations since they can suppress the ionization of the analyte molecules.…”

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confidence: 99%

Determination of pharmaceutical compounds in aqueous dimethyl sulfoxide by electrospray ionization mass spectrometry

Borges

Henion

2005

Rapid Comm Mass Spectrometry

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Standard solutions of reserpine, dextromethorphan, imipramine and amitriptyline in dimethyl sulfoxide (DMSO), DMSO containing 0.1% formic acid, and DMSO/H(2)O (1:1, v/v) containing 0.1% formic acid were analyzed by positive electrospray ionization mass spectrometry (ESI-MS). A triple-quadrupole mass spectrometer equipped with a TurboIonspray (TIS) interface was used for the ESI-MS analyses. The samples dissolved in the respective DMSO solution were infused directly into the mass spectrometer at 10 microL/min using an infusion pump. The positive Q1 full-scan (m/z 50-650) mass spectrum of DMSO (MW = 78) showed three main peaks at m/z 79, 101 and 179, corresponding to the protonated molecule [DMSO+H](+), and the sodiated adducts [DMSO+Na](+) and [2DMSO+Na](+), respectively. The ESI of the compounds in DMSO and DMSO containing 0.1% formic acid was promoted by using the TIS gas (GS2) combined with the nebulizer gas (GS1), and TIS source temperature set to 250 degrees C. In contrast, samples dissolved in DMSO/H(2)O (1:1, v/v) containing 0.1% formic were sprayed at a lower temperature (100 degrees C) using only the nebulizer gas. The TIS voltage (V) was optimized in order to establish the lowest voltage necessary to achieve optimum ESI of each pharmaceutical compound with the voltage maintained below the onset potential required to produce a corona discharge at the TIS probe (sprayer). Detection limits of 10 ng/mL were achieved for reserpine, dextromethorphan, imipramine and amitriptyline in each solvent composition.

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Electrospray mass spectrometry using potassium iodide in aprotic organic solvents for the ion formation by cation attachment

Cited by 32 publications

References 9 publications

A Study of Cation Attachment to Polystyrene by Means of Matrix-assisted Laser Desorption/Ionization and Electrospray Ionization-Mass Spectrometry

A Study of Cation Attachment to Polystyrene by Means of Matrix-assisted Laser Desorption/Ionization and Electrospray Ionization-Mass Spectrometry

Practical implications of some recent studies in electrospray ionization fundamentals

Determination of pharmaceutical compounds in aqueous dimethyl sulfoxide by electrospray ionization mass spectrometry

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